PR libstdc++/77356

PR libstdc++/77356

	* include/bits/regex_compiler.tcc(_M_insert_bracket_matcher,
	_M_expression_term): Modify to support dash literal.
	* include/bits/regex_scanner.h: Add dash as a token type to make
	a different from the mandated dash literal by escaping.
	* include/bits/regex_scanner.tcc(_M_scan_in_bracket): Emit dash
	token in bracket expression parsing.
	* testsuite/28_regex/regression.cc: Add new testcases.

(cherry-picked from commit 6f2116bed6e87668a914dc27fff34c7a68576d4e)

Change-Id: I8f516ef995f0fb7db479c441c9e7714bab518806
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@239794 138bc75d-0d04-0410-961f-82ee72b054a4