We already have a definition for the Czech locale name in
platform_support.h. Use this one instead.
While there, respect the common format of the tests. For most other
tests it's the case that test_iterators.h is placed right underneath the
other #includes (without an empty line). platform_support.h is included
after an empty line.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@232383 91177308-0d34-0410-b5e6-96231b3b80d8