bugfix: sregex-cli: regex parsing error handling had minor issues.
tests: when the env TEST_SREGEX_FORCE_MULTI_REGEXES is set to a true value, the test scaffold will enforce multi-regexes mode for all the test cases that are not.
bugfix: Pike VM: the "pending_matched" output argument was broken in the (new) multi-regexes mode. refactor: pike VM: the "pending_matched" output argument now only provides the first two offset slots (i.e., the "$&" capturing only).