Avoid C compiler warnings that occur when using clang with -Wall.

Except where noted otherwise below most of these warnings relate to implicit
conversions between 64- and 32-bit integers or the signedness of integers
differing in spots.

library/construct.m:
	Delete an unused local variable in the implementation of get_functor_lex.

library/bitmap.m:
	The function MR_bitmap_cmp returns an MR_Integer not an int.

library/thread.semaphore.m:
	Change the count field of the ML_SEMAPHORE_STRUCT structure into
	an MR_Integer (which is what gets passed in).

trace/mercury_trace_declarative.c:
	Avoid a warning about fprintf being called where its second argument
	is not a string literal.  (In this case it can be replaced by a call
	to fputs.)

library/io.m:
mdbcomp/rtti_access.m:
trace/mercury_trace.c:
trace/mercury_trace_cmd_breakpoint.c:
trace/mercury_trace_cmd_help.c:
trace/mercury_trace_completion.m:
trace/mercury_trace_declarative.[ch]:
trace/mercury_trace_external.c:
trace/mercury_trace_internal.c:
trace/mercury_trace_source.c:
trace/mercury_trace_tables.c:
trace/mercury_trace_vars.c:
util/info_to_mdb.c:
util/mfiltercc.c:
util/mdemangle.c:
util/mkinit.c:
util/mkinit_erl.c:
util/mkinit_common.h:
util/mkinit_common.c:
	As above.