Appveyor CI for Windows MSVS build

Add a .gyp file for building all windows tools, and add hook to run gyp
to create corresponding .sln files.

This doesn't try to build for platform:x64.  This fails due to various
errors caused by the assumption that size_t can be converted to an unsigned
int without loss of information, which is not true on Windows x64 (LLP64),
where size_t is 64 bits, but int is only 32 bits.

There are test failures.  client_tests failures are as described in [1].
dump_syms_unittest are as discussed in the description of [2].

[1] https://bugs.chromium.org/p/google-breakpad/issues/detail?id=520
[2] https://codereview.chromium.org/1782453003

BUG=

Change-Id: I965244eb3746f87f30160fd0577e1cc9eb7a8b08
Reviewed-on: https://chromium-review.googlesource.com/441026
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Cr-Mirrored-From: https://chromium.googlesource.com/breakpad/breakpad
Cr-Mirrored-Commit: d4676b89a0751773fdaa2affe08ed28ebdd47a9a

• tools/windows/tools_windows.gyp[Added - diff]