libstdc++: Add support for '?' in linker script globs

libstdc++: Add support for '?' in linker script globs

The scripts/make_exports.pl script used for darwin only replaces '*'
wildcards in globs, it doesn't handle '?'. This means the recent changes
to std::__timepunct exports broke darwin.

Rather than use mangled names in the linker script, this adds support
for '?' to the perl script.

This also removes some unnecessary escaping of the replacement strings
in s// substitutions.

libstdc++-v3/ChangeLog:

	* scripts/make_exports.pl: Replace '?' with '.' when turning
	a glob into a regex.