glamor: Fix uxa-entry point for ImageText16

Was interpreting the incoming chars as 8-bits instead of 16-bits,
resulting in the wrong characters being drawn.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
glamor: Work around libXfont when it fails to use defaultChar

GetGlyphs is supposed to always return the full list of characters
when there is a default character available. However, if an
application opens a 16-bit two dimensional font and then draws with
8-bit requests, the bitmapGetGlyphs function in libXfont versions up
through 1.4.7 will return zero glyphs if there is no 0th row.

While this is a bug in libXfont and should be fixed there, it's easy
to protect glamor from it by simply falling through to the case that
handles GetGlyphs failures for fonts without a default character.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
glamor: Publish change_window_attributes and copy_window

Because uxa doesn't just use glamor directly, it keeps these two
functions from being wrapped so that they get called
automatically. Publishing these will allow uxa to call them directly.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>