Change initialization of mbstate_t objects in tests from '= {0}' to '= {}', which does the same thing, w/o having clang and gcc warn with -Wall.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@247695 91177308-0d34-0410-b5e6-96231b3b80d8
19 files changed