- don't patch away upstream's INCLUDEDIR/LIBDIR mechanism to replace
it with something using CPPFLAGS/LDFLAGS which does exactly the same;
simplifies the patch
- building the targets chosen for the port requires a compiler with
128-bit int support; afaik this requires clang, or GCC 4.6 or newer,
and a 64-bit arch. So I've set the compiler and restricted archs.
(alternatively we could use "ALL_TARGETS=lrs64" on those archs but that
would mean extra mess with arch-specific PLISTs).
- simplify the test target
