[Pixman] MIPS over_n_8888_8888_ca and over_n_8888_0565_ca routines.

Added optimizations for over_n___ca and over_n__0565_ca routines. Benchmark results (lowlevel-blt-bench and cairo-perf-trace) on Malta board (@1Ghz) are included in the log message. Any comments to this patch are welcome. ___ Pixman mailing

[Pixman] [PATCH] MIPS: DSPr2: Added over_n_8888_8888_ca and over_n_8888_0565_ca fast paths.

From: Nemanja Lukic Performance numbers before/after on MIPS-74kc @ 1GHz Referent (before): lowlevel-blt-bench: over_n___ca = L1: 8.32 L2: 7.65 M: 6.38 ( 51.08%) HT: 5.78 VT: 5.74 R: 5.84 RT: 4.39 ( 37Kops/s) over_n__0565_ca = L1: 7.40 L2: 6.95 M: