libstdc++: Set dg-timeout-factor for some slow tests

libstdc++: Set dg-timeout-factor for some slow tests

These tests are very, very slow to compile. If the testsuite is run with
a low tool_timeout value they are likely to fail. By adding a
multiplication factor to those tests, it's still possible to use a low
timeout without spurious failures.

libstdc++-v3/ChangeLog:

	* testsuite/28_regex/algorithms/regex_match/basic/string_range_01_03.cc:
	Add dg-timeout-factor directive.
	* testsuite/28_regex/algorithms/regex_match/cstring_bracket_01.cc:
	Likewise.
	* testsuite/28_regex/algorithms/regex_match/ecma/char/backref.cc:
	Likewise.
	* testsuite/28_regex/algorithms/regex_match/ecma/wchar_t/63199.cc:
	Likewise.
	* testsuite/28_regex/algorithms/regex_match/ecma/wchar_t/anymatcher.cc:
	Likewise.
	* testsuite/28_regex/algorithms/regex_match/ecma/wchar_t/cjk_match.cc:
	Likewise.
	* testsuite/28_regex/algorithms/regex_match/ecma/wchar_t/hex.cc:
	Likewise.
	* testsuite/28_regex/algorithms/regex_match/extended/wstring_locale.cc:
	Likewise.
	* testsuite/28_regex/algorithms/regex_search/61720.cc: Likewise.
	* testsuite/28_regex/algorithms/regex_search/ecma/assertion.cc:
	Likewise.
	* testsuite/28_regex/algorithms/regex_search/ecma/string_01.cc:
	Likewise.
	* testsuite/28_regex/basic_regex/ctors/deduction.cc: Likewise.