Try to get readability-deleted-default.cpp to pass on Windows.

In MS compatibility mode, "extern inline void g()" is not a redundant
declaration for "inline void g()", because of redeclForcesDefMSVC()
(see PR19264, r205485).

To fix, run the test with -fms-compatiblity forced on and off
and explicit check for the differing behavior for extern inline.

Final bit of PR43593.

Differential Revision: https://reviews.llvm.org/D68640

llvm-svn: 374103