* Unify the capitalization across all user-visible error messages (fatal errors, assertion failures, precondition failures) produced by the runtime, standard library and the compiler.
* Update some more tests to the new expectations.
- CYGWIN symbol is used to distinguish Cygwin environment from other OS
and other environment in Windows.
- Added windows and windowsCygnus to OSVersion in StdlibUnittest
If a child process crashes outside of a test context, the parent process
should signal test failure. This behavior is a sign of something bad
happening in the child (for example, memory corruption), and should not
go unnoticed.
