Implement ppa transform bit

**NOTE** This pull request is built on top of the Google Mock pull request. Originally I thought I had sent that base request out on Monday, but I sent it to adhoc-bobcat/regal instead of p3/regal.

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Implement glPopAttrib(GL_TRANFORM_BIT)

Extend the existing RegalPPa/RegalState functionality to add support for
saving and restoring the server side transform state.

Unlike the other emulated functionlity in RegalState, the code I added
does minimize the state transitions, which is especially a good idea if
the backend does not support certain state (such as clip planes) that
may not be actually set by the Regal client.

Extends the testRegalState test to fully cover the new state code. Adds
a quick test for the PushAttrib/PopAttrib calls.

Half of the fix for Regal Issue #27.