a3xx: few more tex fields from test-mipmap
a3xx: add alpha-test bitfields

Note: alpha-test seems to cause EARLY_Z_ENABLE bit to be set, which
doesn't make too much sense.  More likely this is a disable bit.

Note: had to hack up a gles1 yuv texture test, gles2 blob driver doesn't
seem to handle alpha-test ref value properly.
demsm: handle banked context registers

Most of the GL state registers appear to be banked, with two copies
showing up in register dumps (second copy offset by 0x1000).  This seems
to be similar to the banked registers in radeon.
a3xx: updates after tests with glFrontFace()