Missing include for compiling trunk on

I got an error about an invalid forward declaration when compiling
from trunk. This only happened under ArchLinux with gcc-4.3, not
with Ubuntu and gcc-4.2. Adding the include for fl_DocLayout.h to
xap_UnixFrameImpl.cpp solves the problem. I see that someone else
already fixed ie_exp_PDF.cpp which had the same problem.

Bobby