Bug#45288: pb2 returns a lot of compilation warnings on linux

Fix warnings flagged by the new warning option -Wunused-but-set-variable
that was added to GCC 4.6 and that is enabled by -Wunused and -Wall. The
option causes a warning whenever a local variable is assigned to but is
later unused. It also warns about meaningless pointer dereferences.

client/mysql.cc:
  Meaningless pointer dereferences.
client/mysql_upgrade.c:
  Check whether reading from the file succeeded.
extra/comp_err.c:
  Unused.
extra/yassl/src/yassl_imp.cpp:
  Skip instead of reading data that is discarded.
include/my_pthread.h:
  Variable is only used in debug builds.
include/mysys_err.h:
  Add new error messages.
mysys/errors.c:
  Add new error message for permission related functions.
mysys/mf_iocache.c:
  Variable is only checked under THREAD.
mysys/my_copy.c:
  Raise a error if chmod or chown fails.
mysys/my_redel.c:
  Raise a error if chmod or chown fails.
regex/engine.c:
  Use a equivalent variable for the assert.
server-tools/instance-manager/instance_options.cc:
  Unused.
sql/field.cc:
  Unused.
sql/item.cc:
  Unused.
sql/log.cc:
  Do not ignore the return value of freopen: only set buffer if
  reopening succeeds.
  
  Adjust doxygen comment to the right function.
  
  Pass message lenght to log function.
sql/mysqld.cc:
  Do not ignore the return value of freopen: only set buffer if
  reopening succeeds.
sql/partition_info.cc:
  Unused.
sql/slave.cc:
  No need to set pointer to the address of '\0'.
sql/spatial.cc:
  Unused. Left for historical purposes.
sql/sql_acl.cc:
  Unused.
sql/sql_base.cc:
  Pointers are always set to the same variables.
sql/sql_parse.cc:
  End statement if reading fails.
  
  Store the buffer after it has actually been updated.
sql/sql_repl.cc:
  No need to set pointer to the address of '\0'.
sql/sql_show.cc:
  Put variable under the same ifdef block.
sql/udf_example.c:
  Set null pointer flag appropriately.
storage/csv/ha_tina.cc:
  Meaningless dereferences.
storage/example/ha_example.cc:
  Return the error since it's available.
storage/myisam/mi_locking.c:
  Remove unused and dead code.

extra/comp_err.c

@@ -831,7 +831,6 @@ static struct message *parse_message_string(struct message *new_message,
 static struct errors *parse_error_string(char *str, int er_count)
 {
   struct errors *new_error;
-  char *start;
   DBUG_ENTER("parse_error_string");
   DBUG_PRINT("enter", ("str: %s", str));
 
@@ -842,7 +841,6 @@ static struct errors *parse_error_string(char *str, int er_count)
     DBUG_RETURN(0);				/* OOM: Fatal error */
 
   /* getting the error name */
-  start= str;
   str= skip_delimiters(str);
 
   if (!(new_error->er_name= get_word(&str)))

extra/yassl/src/yassl_imp.cpp

@@ -884,21 +884,19 @@ void Alert::Process(input_buffer& input, SSL& ssl)
         else
             hmac(ssl, verify, data, aSz, alert, true);
 
-        // read mac and fill
+        // read mac and skip fill
         int    digestSz = ssl.getCrypto().get_digest().get_digestSize();
         opaque mac[SHA_LEN];
         input.read(mac, digestSz);
 
         if (ssl.getSecurity().get_parms().cipher_type_ == block) {
             int    ivExtra = 0;
-        opaque fill;
 
             if (ssl.isTLSv1_1())
                 ivExtra = ssl.getCrypto().get_cipher().get_blockSize();
             int padSz = ssl.getSecurity().get_parms().encrypt_size_ - ivExtra -
                         aSz - digestSz;
-        for (int i = 0; i < padSz; i++) 
-            fill = input[AUTO];
+            input.set_current(input.get_current() + padSz);
         }
 
         // verify
@@ -981,17 +979,17 @@ output_buffer& operator<<(output_buffer& output, const Data& data)
 void Data::Process(input_buffer& input, SSL& ssl)
 {
     int msgSz = ssl.getSecurity().get_parms().encrypt_size_;
-    int pad   = 0, padByte = 0;
+    int pad   = 0, padSz = 0;
     int ivExtra = 0;
 
     if (ssl.getSecurity().get_parms().cipher_type_ == block) {
         if (ssl.isTLSv1_1())  // IV
             ivExtra = ssl.getCrypto().get_cipher().get_blockSize();
         pad = *(input.get_buffer() + input.get_current() + msgSz -ivExtra - 1);
-        padByte = 1;
+        padSz = 1;
     }
     int digestSz = ssl.getCrypto().get_digest().get_digestSize();
-    int dataSz = msgSz - ivExtra - digestSz - pad - padByte;   
+    int dataSz = msgSz - ivExtra - digestSz - pad - padSz;
     opaque verify[SHA_LEN];
 
     const byte* rawData = input.get_buffer() + input.get_current();
@@ -1020,14 +1018,10 @@ void Data::Process(input_buffer& input, SSL& ssl)
             hmac(ssl, verify, rawData, dataSz, application_data, true);
     }
 
-    // read mac and fill
+    // read mac and skip fill
     opaque mac[SHA_LEN];
-    opaque fill;
     input.read(mac, digestSz);
-    for (int i = 0; i < pad; i++) 
-        fill = input[AUTO];
-    if (padByte)
-        fill = input[AUTO];    
+    input.set_current(input.get_current() + pad + padSz);
 
     // verify
     if (dataSz) {
@@ -2073,11 +2067,9 @@ void Finished::Process(input_buffer& input, SSL& ssl)
         if (ssl.isTLSv1_1())
             ivExtra = ssl.getCrypto().get_cipher().get_blockSize();
 
-    opaque fill;
     int    padSz = ssl.getSecurity().get_parms().encrypt_size_ - ivExtra -
                      HANDSHAKE_HEADER - finishedSz - digestSz;
-    for (int i = 0; i < padSz; i++) 
-        fill = input[AUTO];
+    input.set_current(input.get_current() + padSz);
 
     // verify mac
     if (memcmp(mac, verifyMAC, digestSz)) {