The bit that indicates that the base size is set is
XCB_ICCCM_SIZE_HINT_BASE_SIZE. However, instead this code checked
XCB_ICCCM_SIZE_HINT_P_SIZE which is set to indicate how the initial window
position is chosen. So we were checking the complete wrong bit. Whoops...
Fixes: https://github.com/awesomeWM/awesome/issues/456
Signed-off-by: Uli Schlachter <psychon@znc.in>