[PATCH] Enable all targets on Windows (MSVC)

[Tim Northover]

> Generally, looks reasonable to me. Do you have any numbers of hand,
> though? E.g. differences in build times?

A quick set of tests building check-all LLVM+Clang (Debug, MSVC 2010
on the Windows side) gives:

Windows:
X86: 50 minutes
all: 61 minutes
= 22% longer

Linux:
X86: 38 minutes
all: 44 minutes
= 19% longer

Tim.