Implement sceFontGetShadowGlyphImage().

Not sure if any games actually use it, though...
Use the correct default for font altCharCode.
Oops, fix negative clip regions.

Since they're summed, need to clamp the left/top side.  And the
bottom/right side is offset by x/y.
Reflect font altCharCode in psp mem for tests.

Makes it easier to be sure it's working right.  Not completely impossible
a game will check it... but hopefully not.
Fix sceFontSetResolution() error codes.
Fix error handling in sceFontPointToPixelH()/etc.
Cleanup errors in sceFontGet*ImageRect().
Implement sceFontGetShadowInfo().
Fix results of sceFontGetFontInfo() for user fonts.
Correct sceFontGetFontInfoByIndexNumber().

It just gets font style info, pretty simple.
Fix sceFontGetFontList() error codes.
Improve error checking in sceFontGetNumFontList().
Fix nearest size check in optimum, cleanup.
Merge pull request #5581 from unknownbrackets/font

Correct a bunch of sceFont functions, shadows, etc.