Prefer compile-time checks to QSKIP.

Prefer compile-time checks to QSKIP.

Qt has compile-time defines for determining the presence of each style
in the build.  Use these to exclude inapplicable test data instead of
including all test data and then being unable to distinguish the absence
of a style from regressions in QStyleFactory.

Change-Id: Iab1756aec80892a8b587bb635779537c64b1d4dd
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>