[AD] More asserts

[Jon Rafkind <workmin@xxxxxxxxxx>]

Sorry for not sending these in sooner.

Attached are some asserts for graphics.c and quat.c. ASSERT seems necessary when the pointer in question is necessary for the function to continue. Some functions in graphics.c need the system_driver, but only for one line. At these times, I added an extra if clause and not ASSERT( system_driver ). I wasnt sure if system_driver is gauranteed to exist or not, but I saw an ASSERT in another function and decided to go through and add the rest.

All diff files made from allegro-4.1.11 source.

Attachment: graphics.c.diff
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Attachment: quat.c.diff
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