.gitignore lib/python build artifacts

../lib/python/gremlin_view.py
../lib/python/pyngcgui.py
Makefile.modinc: add KERNEL_MATH_CFLAGS back to EXTRA_CFLAGS

Left out somewhere along universal build development
rtapi/Submakefile:  add correct -rpath after $(EMC2_RTLIB_DIR) change
Makefile.inc:  Fix KBUILD_EXTRA_SYMBOLS for out-of-tree module builds

Fixes symbols.[01] unit tests