pkgconfig spkg
Merge branch 'pkgconfig' into toplevel
move pkgconfig in the right spot
python-sage: whitelist python2.7 multiprocessing in stackframes test
python-sage: comment on header hack
python-sage: make libgap obsolete (I)
python-sage: make libgap obsolete, II (patches against gap upstream)
cython: add -MF switch to write dependency files (#14728)

... and -M -F -D -P
cython: patch: gdb output dir option
sage-doc: build system
sage-doc. use SAGE_DOC_SRC as doc source path

this is required if srcdir!=builddir. otherwise it doesn't make a
difference
sage-bin: env

- adapt env
- remove sage-arch-env
sage-bin: remove ECLDIR from env.sh (ecl takes care of it)
sage-bin: sage-build
sage-bin: sage-spkg.in
sage-bin: sage.in

- config files to SAGE_ETC=@sysconfdir@
- cleanup
- PIPESTATUS_CMD
sage-bin: simplify sage-sdist
sage-bin: disable SAGE_ROOT relocation warning. fix later
atlas: spkg

- checksum roulette
- correctly locate external tarball
- spkg-check wrapper
- atlas: chmod +w
boehm_gc: spkg-install