os: Eliminate uninitialized value warnings from access.c

The ConvertAddr function doesn't reliably set the 'addr' return value,
and so callers are getting flagged for using potentially uninitialized
values. Initialize the value in the callers to NULL and then go ahead
and check for NULL values before using them.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
xkb: Initialize 'bad' Atom in _XkbSetNamesCheck

When _XkbCheckAtoms returns NULL for an error, it always sets the
error return code, but GCC can't figure that out, so just initialize
the local variable, 'bad', in _XkbSetNamesCheck to eliminate the warning.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
composite: Wrap GetSpans

GetSpans should flush composition from children to parent, just like
GetImage and SourceValidate.  Fortunately no one is likely to have
noticed, since to hit this you're already deep into failure town.

Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Keith Packard <keithp@keithp.com>