middle-end/117801 - failed register coalescing due to GIMPLE schedule

For a TSVC testcase we see failed register coalescing due to a
different schedule of GIMPLE .FMA and stores fed by it.  This
can be mitigated by making direct internal functions participate
in TER - given we're using more and more of such functions to
expose target capabilities it seems to be a natural thing to not
exempt those.

Unfortunately the internal function expanding API doesn't match
what we usually have - passing in a target and returning an RTX
but instead the LHS of the call is expanded and written to.  This
makes the TER expansion of a call SSA def a bit unwieldly.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

The ccmp changes have likely not seen any coverage, the debug stmt
changes might not be optimal, we might end up losing on replaceable
calls.

	PR middle-end/117801
	* tree-outof-ssa.cc (ssa_is_replaceable_p): Make
	direct internal function calls replaceable.
	* expr.cc (get_def_for_expr): Handle replacements with calls.
	(get_def_for_expr_class): Likewise.
	(optimize_bitfield_assignment_op): Likewise.
	(expand_expr_real_1): Likewise.  Properly expand direct
	internal function defs.
	* cfgexpand.cc (expand_call_stmt): Handle replacements with calls.
	(avoid_deep_ter_for_debug): Likewise, always create a debug temp
	for calls.
	(expand_debug_expr): Likewise, give up for calls.
	(expand_gimple_basic_block): Likewise.
	* ccmp.cc (ccmp_candidate_p): Likewise.
	(get_compare_parts): Likewise.