Remove unused regex code

Remove unused regex code

This effectively reverts the parts of commit
01d9015868088fc3347511a095dce0195751c530 which add those sources

That commit also adds -fno-builtin-sscanf to CXXFLAGS. Probably that is part of
the same change, but I don't know for sure, so I've left that alone.

	* Makefile.am (AM_CPPFLAGS): Remove regex from include path.
	(@SETUP@_SOURCES): Remove regex.c.
	* regex/config.h: Delete file.
	* regex/re_comp.h: Delete file.
	* regex/regcomp.c: Delete file.
	* regex/regex.c: Delete file.
	* regex/regex.h: Delete file.
	* regex/regex_internal.c: Delete file.
	* regex/regex_internal.h: Delete file.
	* regex/regexec.c: Delete file.

Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>