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>

DEPS

@@ -69,6 +69,13 @@ hooks = [
                "--no-circular-check",
                "src/src/client/windows/breakpad_client.gyp"],
   },
+  {
+    # XXX: this and above should all be wired into build/all.gyp ?
+    "action": ["python",
+               "src/src/tools/gyp/gyp_main.py",
+               "--no-circular-check",
+               "src/src/tools/windows/tools_windows.gyp"],
+  },
   {
     # Keep the manifest up to date.
     "action": ["python", "src/src/tools/python/deps-to-manifest.py",