preproc.py script from another project. Had to further develop it to
get around the amazingly complicated preprocessor usage in the scmos
subdirectory. Needed to add handling of parameterized definitions;
could not figure out how to align the syntax used in scmos/extract_template
with any consistent syntax. Gave up and rewrote some of the contents of
extract_template to avoid the more ambiguous usage. All of this is to
support a completely deprecated scmos.tech. However, it does avoid both
the M4 and cpp preprocessors altogether. Also did auto-detection of
python3 in the configure script for use of the preproc.py preprocessor,
and applied the same preprocessor to the macro definitions.
2db6a6849a