win handler: Provide a wmain() entry point
win handler: Provide a wmain() entry point

Crashpad’s own build always uses wWinMain(), the default entry point for
/subsystem:windows, producing crashpad_handler.exe. crashpad_handler.com
is a /subsystem:console version produced by running editbin on a copy of
crashpad_handler.exe. This leaves the entry point intact, so both copies
use wWinMain(). crashpad_handler.com does not use wmain() as
traditionally used by /subsystem:console programs.

For the in-Chromium build’s tests, it is conveient to produce the
/subsystem:console version, crashpad_handler.com, directly as linker
output, as opposed to using editbin to transform a /subsystem:windows
version. This /subsystem:console version uses the normal wmain() entry
point.

By providing both wWinMain() and wmain(), both build types can be
accommodated.

Bug: chromium:779790
Change-Id: Ieb784db0cc245c6e4c12fb1dd83b8b95e159bdec
Reviewed-on: https://chromium-review.googlesource.com/746161
Reviewed-by: Leonard Mosescu <a498b187a5d2699f346338eaceae9af4ef9cb2c6@chromium.org>

atom/crashpad,atom/crashpad,chromium/crashpad,chromium/crashpad,atom/crashpad,chromium/crashpad