Add homogeneous point mapping to Matrix

Add homogeneous point mapping to Matrix

Adds mapping of homogeneous points (points with three scalar components,
where the last component is not 1). Includes fix for tests when
running on 32 bit debug builds

BUG=
R=bsalomon@google.com

Committed: https://code.google.com/p/skia/source/detail?r=10755

[egdaniel, 2013-08-14 14:32:57]

In the previous version, its was the ubuntu and chrome x86 debug tests that
failed. Those tests passed the trybots on this CL

[bsalomon, 2013-08-14 14:36:21]

lgtm

[egdaniel, 2013-08-15 21:12:18]

Committed patchset #1 manually as r10755 (presubmit successful).