Removed some unneeded variables and comparisons

src/interfaces/ecpg/ecpglib/execute.c

src/interfaces/ecpg/ecpglib/extern.h

src/interfaces/ecpg/ecpglib/prepare.c

src/interfaces/ecpg/include/ecpglib.h

src/interfaces/ecpg/pgtypeslib/datetime.c

src/interfaces/ecpg/pgtypeslib/dt.h

src/interfaces/ecpg/pgtypeslib/dt_common.c

src/interfaces/ecpg/pgtypeslib/interval.c

src/interfaces/ecpg/pgtypeslib/timestamp.c

src/interfaces/ecpg/test/expected/sql-code100.c

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

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

src/interfaces/ecpg/test/sql/code100.pgc

src/interfaces/ecpg/test/thread/alloc.pgc

src/interfaces/ecpg/test/thread/descriptor.pgc