Inline frequently called functions.

src/backend/access/common/heapvalid.c

src/backend/access/heap/heapam.c

src/backend/commands/trigger.c

src/backend/storage/buffer/buf_init.c

src/backend/storage/buffer/bufmgr.c

src/backend/storage/ipc/Makefile

src/backend/storage/ipc/ipc.c

src/backend/storage/ipc/s_lock.c

src/backend/storage/ipc/spin.c

src/backend/storage/lmgr/lock.c

src/backend/utils/cache/catcache.c

src/include/access/valid.h

src/include/c.h

src/include/storage/ipc.h

src/include/storage/s_lock.h

src/include/storage/spin.h