Adds WM_STRUT_PARTIAL support (minimal) to make applications work properly that set WM_STRUT_PARTIAL but not WM_STRUT.
This patch only takes heed of the left, right, top, bottom arguments of the WM_STRUT_PARTIAL as the original WM_STRUT code did.
The patch is against fluxbox 1.1.1.
WM_STRUT_PARTIAL support