* include/bits/regex.h (regex_match<>, regex_search<>):
Change regex_executor caller. Now use their return value instead
of checking __m[0].matched to find out if it's successful.
(regex_search<>): Move the search logic to regex_executor.
* include/bits/regex_automaton.h: Add some new _Opcode. Refactor
_NFA::_M_insert_*.
* include/bits/regex_automaton.tcc: Add DEBUG dump for new
_Opcode. Refactor _NFA::_M_insert_*.
* include/bits/regex_compiler.h (_Compiler<>::_M_get_nfa):
Use make_shared instead of construct by hand.
* include/bits/regex_compiler.tcc: Implement _Compiler<>::_M_assertion.
* include/bits/regex_constants.h: Fix indentation and line breaking.
* include/bits/regex_executor.h: Add _ResultsEntry to support
greedy/ungreedy mode. Move regex_search logic here.
* include/bits/regex_executor.tcc: Implement assertions and
greedy/ungreedy matching.
* include/bits/regex_scanner.h: Add a new token _S_token_ungreedy.
* include/bits/regex_scanner.tcc: Parse a new token _S_token_ungreedy.
* testsuite/28_regex/algorithms/regex_search/ecma/assertion.cc: New.
* testsuite/28_regex/algorithms/regex_search/ecma/greedy.cc: New.
* testsuite/28_regex/algorithms/regex_search/ecma/string_01.cc:
Fix comment.