[Pixman] Basic infrastructure for MIPS architecture and initial set of SRC routines.

[Nemanja Lukic]

Per previous code review:

Run time detection is changed so that "MIPS 74K" instead of "MIPS 74Kc" string
is searched in /proc/cpuinfo. I used 74Kc as search string, since all boards I
have, although Kf (like 24Kf, 34Kf, 74Kf, 1004Kf) had in their name Kc with FPU
string added, like this (where pure Kc cores don't have that FPU part):
 - MIPS 24Kc V7.12  FPU V0.0
Added macros for LEAF/END declarations for the assembler functions:
 - LEAF_MIPS32R2 that declares entry point of MIPS32r2 function (like memcpy).
 - LEAF_MIPS_DSPR2 that declares entry point of DSPr2 function.
 - END is the same for both function types.
-mdspr2 CFLAG is not forced for MIPS optimizations, and now it is not needed
for the succesfull build.

Best Regards,
Nemanja Lukic