Add C++ library interface data

Add C++ library interface data

This patch adds a CSV file with information about the API of the
standard C++ library.  This information can be used in multiple ways.
So far there are two use cases:

- to generate the module export list for the standard C++ library
- to create the name hints to compiler emits when symbols in the
  std namespace are not found

Adding more uses can be easily done by potentially adding more columns
to the CSV file and adding to the Python script which generates the
output file.

contrib/
2022-10-18  Jonathan Wakely   <jwakely@redhat.com>
	    Ulrich Drepper  <drepper@redhat.com>

	* gcc_update: Add rule for gcc/cp/std-name-hint.gperf.

gcc/cp/
2022-10-18  Jonathan Wakely   <jwakely@redhat.com>
	    Ulrich Drepper  <drepper@redhat.com>

	* Make-lang.in: Add rules to generate std-name-hint.gperf.  Adjust
	rule to generate std-name-hint.h to allow chain rule.
	* std-name-hint.h: Regenerated.
	* std-name-hint.gperf: This file is now generated.
	* cxxapi-data.csv: New file.  CSV file with C++ API data.
	* gen-cxxapi-file.py: New file.  Generate std-name-hint.gperf
	and module export source (in future).