This patch fixes the MinGW Makefile:
- Adds support for the keystroke DLL.
DLLs are interchangeable between gcc and msc builds.
- Gets the Makefile to work for Win95 and friends
- Adds the -mms-bitfields flag to ensure savefile compatibility between
MinGW and MSC files
- Fixes various minor issues: layout, make spotless, and some duplicate
commands that are now governed by a new tag ($(O)gamedir.tag).
f5a1d78fee