[AD] Fixing a pair of trivial warnings in Allegro 4.4

[Boon947 <guild.wars.account@xxxxxxxxxx>]

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Hello,

I've posted this patch to the forums, but the discussion seems
to have died down. Is the mailing list a better place to discuss
patches?

The attached patch fixes a pair of trivial warnings in Allegro 4.4

I also noticed a warning about an aliasing problem in the OSS code;
with compilers becoming more aggressive at high optimization levels,
it might be prudent to add -fno-strict-aliasing to the CFLAGS, as
Linux has been doing for ages.

Regards.

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