Aria service threads are created "joinable", but they're not "joined" on
completion. This causes memory leaks around thread local storage.
Fixed by joining service thread. Simplified relevant code and cleaned up
relevant valgrind suppressions.
storage/maria/CMakeLists.txt:
Added files of service thread framework.
storage/maria/Makefile.am:
Added files of service thread framework.
storage/maria/ma_checkpoint.c:
Separated service thread framework.
storage/maria/ma_servicethread.c:
Added files of service thread framework.
storage/maria/ma_servicethread.h:
Added files of service thread framework.