WL#5030: Split and remove mysql_priv.h

This patch:

- Moves all definitions from the mysql_priv.h file into
  header files for the component where the variable is
  defined
- Creates header files if the component lacks one
- Eliminates all include directives from mysql_priv.h
- Eliminates all circular include cycles
- Rename time.cc to sql_time.cc
- Rename mysql_priv.h to sql_priv.h

sql/my_decimal.h

@@ -28,10 +28,17 @@
 #ifndef my_decimal_h
 #define my_decimal_h
 
+#if defined(MYSQL_SERVER) || defined(EMBEDDED_LIBRARY)
+#include "sql_string.h"                         /* String */
+#endif
+
 C_MODE_START
 #include <decimal.h>
 C_MODE_END
 
+class String;
+typedef struct st_mysql_time MYSQL_TIME;
+
 #define DECIMAL_LONGLONG_DIGITS 22
 #define DECIMAL_LONG_DIGITS 10
 #define DECIMAL_LONG3_DIGITS 8
@@ -133,6 +140,12 @@ const char *dbug_decimal_as_string(char *buff, const my_decimal *val);
 #define dbug_decimal_as_string(A) NULL
 #endif
 
+bool str_set_decimal(uint mask, const my_decimal *val, uint fixed_prec,
+                     uint fixed_dec, char filler, String *str,
+                     CHARSET_INFO *cs);
+
+extern my_decimal decimal_zero;
+
 #ifndef MYSQL_CLIENT
 int decimal_operation_results(int result);
 #else
@@ -289,7 +302,14 @@ int my_decimal_ceiling(uint mask, const my_decimal *from, my_decimal *to)
 }
 
 
+inline bool str_set_decimal(const my_decimal *val, String *str,
+                            CHARSET_INFO *cs)
+{
+  return str_set_decimal(E_DEC_FATAL_ERROR, val, 0, 0, 0, str, cs);
+}
+
 #ifndef MYSQL_CLIENT
+class String;
 int my_decimal2string(uint mask, const my_decimal *d, uint fixed_prec,
 		      uint fixed_dec, char filler, String *str);
 #endif