libstdc++: Define INSTANTIATE_FACET_ACCESSORS macro in compat source [PR103755]

libstdc++: Define INSTANTIATE_FACET_ACCESSORS macro in compat source [PR103755]

compatibility-ldbl-alt128.cc re-includes locale-inst-numeric.h and
locale-inst-monetary.h but wasn't defining the macros added in
r13-3888-gb3ac43a3c05744.

Put those macros in a new internal header that can be included everywhere
they're used.

libstdc++-v3/ChangeLog:

	PR libstdc++/103755
	* src/c++11/locale-inst-monetary.h: Include new header.
	* src/c++11/locale-inst-numeric.h: Likewise.
	* src/c++11/locale-inst.cc: Likewise.
	(INSTANTIATE_USE_FACET, INSTANTIATE_FACET_ACCESSORS): Move
	macro definitions to ...
	* src/c++11/facet_inst_macros.h: New file.