cleanup libcsage linking

- remove global -lcsage
- s/-lcsage/@CSAGE_LIBS@/
- add missing @CSAGE_LIBS@
- use libtool
- get rid of -L quirks
 gap(I)
fix toplevel sage executable (path to env)
tachyon. make sure "bin" exists, and use spkg-dist-install
clean stamps, still in use ...
flint: create directory before putting file into it
python-sage: more header checks

- ppl
- mpfr
- ratpoints
- mpc
sage-dist-install: target must be directory