I had to make the following changes in the "variables" file in order to
get gmsh to compile with g++ (3.3.3-7)
for FLAGS =
change "-fno-exceptions" to "-fexceptions"
for GMSH_LIBS =
add "-lfltk_images" after "-lfltk"
add "-L/usr/X11R6/lib" in front of "-lX11"