Rework CFLAGS & CXXFLAGS

Allow overriding the optimisation level from the environment.
Add CPPFLAGS, and always add -ffast-math and -fomit-frame-pointer.
Add verbose option to Makefile (V=1)
Simplify platform detection in jaguarcore.mak

Default SYSTYPE to __GCCUNIX__, and change it only for special cases,
instead of the other way around.

Remove SDLLIBTYPE, it wasn't used at all.
Merge remote-tracking branch 'partycle/platform_detect'
Made keyboard handling a bit more sane.

What this means is that now, if there are no gamepads plugged in, it
will add the keyboard as a device plugged into slot #0 (CONTROLLER1).
Also, if you have any devices plugged in it will also honor whatever
choice you have made WRT the keyboard and attempt to connect it to
whichever preferred slot you have set it to.

Assuming testing goes OK, this will be the 2.1.1 release. :-D