* framebuffer: avoid gluint overflow
GLuint was being initialized to -1 and rolling over to unsigned int max,
its defined behaviour but very unnecessery. add a bool and use it for
checking if allocated or not.
* opengl: avoid gluint rollover
-1 rolls over to unsigned int max, use 0xFF instead.
* core: big uint64_t to int type conversion
there were a few uint64_t to int implicit conversions overflowing int
and causing UB, make all monitor/workspaces/windows use the new
typedefs. also fix the various related 64 to 32 implicit conversions
going around found with -Wshorten-64-to-32
