[AArch64] Allow using emulated tls on platforms other than ELF

This matches how it is done on X86.

This allows using emulated tls on windows; in MinGW environments,
native tls isn't supported at the moment.

Set the right Data*bitsDirective for windows to match the existing
tests for other platforms. Make parts of the existing tests a regex,
to allow matching .section .rdata for windows, to avoid having to
duplicate the rest of the tests for windows.

Differential Revision: https://reviews.llvm.org/D40770

llvm-svn: 319644