Xext: fix invalid event type mask in XTestSwapFakeInput
In commit b320ca0f the mask was inadvertently changed from octal 0177 to hexadecimal 0x177.
Fixes commit b320ca0f Xtest: disallow GenericEvents in XTestSwapFakeInput
Found by Stuart Cassoff
Signed-off-by: Peter Hutterer peter.hutterer@who-t.net (cherry picked from commit bb1711b7)
cc @ofourdan