Make most_specific_rval handle mkword_hole.

dupelim.most_specific_rval did not handle the `mkword_hole' option that
was added to the `rval' type.

compiler/dupelim.m:
	Fix the bug.

tests/valid/Mmakefile:
tests/valid/dupelim_mkword_hole.m:
	Add test case.
Fix bug #183

--warn-dead-procs should not emit warnings for procedures that are foreign
exported.  However, for procedures that were foreign exported only to languages
that were *not* supported by the current backend, it did emit warnings.
This was because we only kept track of foreign_export pragmas for languages
that were supported by the current backend.  The fix is to (separately) keep
track of whether there were any foreign_export pragmas at all for a procedure.

compiler/hlds_pred.m:
	Add a new field to the proc_info structure that keeps track
	of whether the were any foreign_export pragmas for the procedure.

compiler/add_pragma.m:
	Fill in the new field.

compiler/dead_proc_elim.m:
	Only emit a warning about a procedure being dead if it is not
	the subject of any foreign_export pragmas.

	Use a more appropriate variable name in a spot.

tests/valid/Mmakefile:
tests/valid/bug183.m:
	Add a regression test for the above.
Update a .gitignore file.

mfilterjavac/.gitignore:
	Ignore .mih files.
More fixes for float.float64_bits_string/1.

The implementation of float64_bits_string/1 does not work correctly on
platforms where sizeof(long) == 4.  This is the case for the i386 version of
NetBSD.  Also, make the code in the float module consistent with the fact the
runtime allows there to be no 64-bit integer type defined at all.

configure.ac:
runtime/mercury_conf.h.in:
	Define a new macro that expands to the integer length modifier for
	the MR_int_least64_t type.

library/float.m:
	Use the new macro to avoid a spot that was assuming that a long is
	a 64-bit quantity.  (TODO: we can probably now simplify some of the
	Windows specific code here, but I don't want to do that until I have
	tested it.)

	Have float64_bits_string/1 call MR_fatal_error() if MR_INT_LEAST64_TYPE
	is not defined.
Merge branch 'version-13_05-branch'