Add '_LIBCPP_ASSERT(ready())' to several match_results method that have this precondtion. Fix several tests which did not honor this precondition. Thanks to Andrey Maksimov for pointing this out.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@359324 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed