Fix broken libsingular-config
Merge pull request #471 from fingolfin/fix-libsingular-config

Fix broken libsingular-config
Use @SINGULAR_CFLAGS@ instead of '-D(SING|OM)_NDEBUG' in lib*-config/*.pc  (according to --enable-debug/--disable-optimization!)

chg: also some minor BS cleanup
Let _configure_ generate desctop/Singular*.desktop
fix: do not test for omGetBackTrace on OsX
add: ncpreim.lib
compare PLIBS with master