Remove QT_NO_KEYWORDS for good

We're now using external libraries that aren't keywords-clean (namely,
Marble).

Signed-off-by: Thiago Macieira <thiago@macieira.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Detect the presence of the missing Marble header by compiling it

Signed-off-by: Thiago Macieira <thiago@macieira.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add a variable for the Marble library name

I need that for a Marble installed somewhere other than the linker's
default search path.

Signed-off-by: Thiago Macieira <thiago@macieira.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>