Share macros/defines between C and Assembly

[ZERICO2005]

We should access the contents of <errno.h> and <fenv.h> in assembly; And perhaps we should also allow some of ti84pceg.inc to be accessible in C as well.

For example:

; <errno.h> defines for assembly
_EPERM           :=  1 ; permission error 
_EINVAL          :=  2 ; invalid argument 
_EIO             :=  3 ; io error 
_EDOM            :=  4 ; math domain error 
_ERANGE          :=  5 ; math range error
; ...

https://pastebin.com/0DKg1Qjm