Add TARGET_IFUNC_REF_LOCAL_OK

Add TARGET_IFUNC_REF_LOCAL_OK

1. On some targets, like PowerPC, reference to ifunc function resolver
must be non-local so that compiler will properly emit PLT call.  Add
TARGET_IFUNC_REF_LOCAL_OK to allow binding indirect function resolver
locally for targets which don't require special PLT call sequence.
2. Add ix86_call_use_plt_p to call local ifunc function resolvers via
PLT.

gcc/

	PR target/51469
	PR target/83782
	* target.def (ifunc_ref_local_ok): Add a target hook.
	* varasm.c (default_binds_local_p_3): Force indirect function
	resolver non-local only if targetm.ifunc_ref_local_ok returns
	false.
	* config/i386/i386-expand.c (ix86_expand_call): Call
	ix86_call_use_plt_p to check if PLT should be used.
	* config/i386/i386-protos.h (ix86_call_use_plt_p): New.
	* config/i386/i386.c (output_pic_addr_const): Call
	ix86_call_use_plt_p to check if "@PLT" is needed.
	(ix86_call_use_plt_p): New.
	(TARGET_IFUNC_REF_LOCAL_OK): New.
	* doc/tm.texi.in: Add TARGET_IFUNC_REF_LOCAL_OK.
	* doc/tm.texi: Regenerated.

gcc/testsuite/

	PR target/51469
	PR target/83782
	* gcc.target/i386/pr83782-1.c: New test.
	* gcc.target/i386/pr83782-2.c: Likewise.