ARMv6: New blit routines

ARMv6: New blit routines

These are usable either as various composite operations, or via the
top-level function pixman_blt() which now does some blitting for the
first time on an ARMv6 platform (previously it just returned FALSE).

src_8888_8888

    Before          After
    Mean   StdDev   Mean   StdDev  Confidence  Change
L1  414.5  9.4      445.8  3.6     100.0%      +7.6%
L2  93.3   20.7     114.5  12.9    100.0%      +22.7%
M   57.0   0.2      89.2   0.5     100.0%      +56.4%
HT  28.7   0.3      39.6   0.4     100.0%      +37.9%
VT  25.5   0.2      35.3   0.4     100.0%      +38.4%
R   20.1   0.1      33.8   0.3     100.0%      +67.8%
RT  7.8    0.2      12.7   0.4     100.0%      +62.7%

src_0565_0565

    Before          After
    Mean   StdDev   Mean   StdDev  Confidence  Change
L1  397.4  6.1      412.5  5.2     100.0%      +3.8%
L2  143.2  10.9     141.9  6.5     68.9%       -0.9%  (insignificant)
M   90.7   0.4      133.5  0.7     100.0%      +47.1%
HT  38.6   0.3      53.7   0.7     100.0%      +39.0%
VT  33.0   0.3      47.3   0.6     100.0%      +43.3%
R   25.7   0.2      42.1   0.5     100.0%      +64.1%
RT  8.0    0.2      13.3   0.3     100.0%      +65.6%

src_8_8

    Before          After
    Mean   StdDev   Mean   StdDev  Confidence  Change
L1  716.5  9.8      768.2  20.4    100.0%      +7.2%
L2  246.2  12.7     260.5  8.8     100.0%      +5.8%
M   146.8  0.7      227.9  0.7     100.0%      +55.2%
HT  44.9   0.6      62.1   1.0     100.0%      +38.2%
VT  35.6   0.4      53.4   0.7     100.0%      +50.0%
R   29.7   0.3      48.2   0.6     100.0%      +62.2%
RT  8.6    0.2      12.9   0.4     100.0%      +49.3%