Log Message:
x11/fltk13: add explicit depends on libxcb and libXcursor

These are otherwise found in a host system and possibly cause trouble.

Note that verifypc still has some suggestions that we might want to
add:

verifypc: fontconfig not a direct dependency
verifypc: freetype2 not a direct dependency
verifypc: x11 not a direct dependency
verifypc: xdmcp not a direct dependency
verifypc: xrender not a direct dependency
verifypc: zlib not a direct dependency