cxsc: strip & fix install names
Add 'make check' target which scans for bad hardcoded paths

I.e. occurrences of the $PREFIX value, or usage of files from Fink.
Makefile: enhance 'clean' and 'distclean' targets
normaliz: link against our GMP, not Fink's
fix_install_names.sh: massively improved

We now consistently use as base rpath the $PREFIX dir. Moreover, the
default LC_RPATH now involves @loader_path, and thus is fully
relocatable. All binaries in the final bundle should now be able to
run when called from an arbitrary directory, not just the PREFIX
directory.

The new script also automatically runs 'strip -S' and has easier calling
conventions. As a result, most install.sh scripts are very short now.
Makefile: 'make check' now also scans for build dir references
bundle: remove unnecessary keys from Info.plist

Some are obsolete, some simple were setting a value identical to the
default value.
bundle: fix calling 'clean' target twice
normaliz: fix path to libnormaliz.dylib in bin/normaliz
pari: cleanup TODO in install.sh
fix_install_names.sh: more aggressively remove bad LC_RPATH values

Some binaries contain more than one LC_RPATH hardcoding the PREFIX,
but we previously replaced at most one. So now, after replacement,
also explicitly delete some typical 'bad' LC_RPATH values.
cxsc: fix rpath usage, no more hard coded paths