avoid reading beyond the end of the line buffer in rubthrough
make sure T1lib anti-aliasing is properly setup for non AA text

Previously t1_aa was initialized to 0, the same as the non-AA setting,
which meant if the first text drawn was non-AA that T1 anti-aliasing
hadn't been configured.

Initialize it to -1, an invalid anti-aliasing setting so that an initial
AA setting of "none" will properly initialize.