[libcxx] Recover no-exceptions XFAILs - I

First batch of changes to get some of these XFAILs working in the
no-exceptions libc++ variant.

Changed some XFAILs to UNSUPPORTED where the test is all about exception
handling. In other cases, used the test macros TEST_THROW and
TEST_HAS_NO_EXCEPTIONS to conditionally exclude those parts of the test
that concerns exception handling behaviour.

Reviewers: EricWF, mclow.lists

Differential revision: https://reviews.llvm.org/D24562

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@283441 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/re/re.regex/re.regex.assign/assign.pass.cpp

@@ -7,7 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: libcpp-no-exceptions
 // <regex>
 
 // template <class charT, class traits = regex_traits<charT>> class basic_regex;
@@ -27,6 +26,7 @@ int main()
     assert(r2.mark_count() == 2);
     assert(std::regex_search("ab", r2));
 
+#ifndef TEST_HAS_NO_EXCEPTIONS
     bool caught = false;
     try { r2.assign("(def", std::regex::extended); }
     catch(std::regex_error &) { caught = true; }
@@ -34,4 +34,5 @@ int main()
     assert(r2.flags() == std::regex::ECMAScript);
     assert(r2.mark_count() == 2);
     assert(std::regex_search("ab", r2));
+#endif
 }