Synced parser and keyword list.

src/interfaces/ecpg/ChangeLog

src/interfaces/ecpg/preproc/keywords.c

src/interfaces/ecpg/preproc/pgc.l

src/interfaces/ecpg/preproc/preproc.y

src/interfaces/ecpg/test/expected/thread-thread.c

src/interfaces/ecpg/test/expected/thread-thread_implicit.c