Windows suggestion to not spawn cmd

[irakhlin]

Hello,

Currently when building as is with mingw64 for windows the resultant stoken-gui.exe will automatically spawn a cmd prompt behind the GUI window. I was able to resolve this issue by changing the following flag in the Makefile after running ./configure.
Change:
CC= x86_64-w64-mingw32-gcc
to
CC= x86_64-w64-mingw32-gcc -02 -Wall -mms-bitfields -mwindows

I believe the only really needed flag is "-mwindows", perhaps it should be added to the preconfigured makefile to be added automatically to all mingw builds.