sage-bin build system and env

- add environment for build
- SAGE64 maybe incomplete
- remove sage-arch-env
- remove MPLCONFIGDIR hack
sage-bin: sage-CSI: unhardcode paths
sage-bin build system continued
python-sage: check whether gprc.expect is available (#14749)

(otherwise subsequent tests will timeout)
python-sage SAGE_ETC (#14750)

- gp.py
- qepcad.py
python-sage: fix relative paths in include statements
python-sage: move files around, turn into templates

(this is to help git keeping track)
python-sage more explicit import/include paths

intended to work with -I<parent_directory_of_'sage'>
python-sage: comment on header hack
python-sage: build system

- BLAS, BLAS2 check
- generate setup.py, module_list.py
- AC_ARG_VAR
- am_check_python_headers
- AM_DEFAULT_EXT globally (?)
- common makefile
  - dependency tracking for cython files
  - some automake global flags
  - some recursive targets
- add all makefiles to AC_OUTPUT
python-sage: move hypellfrob.cpp and planarity.c

(need unique names for hypellfrob.la, planarity.la)
python-sage: module_list

- BLAS
- conditional extensions
- include paths
python-sage s/lib(gap|ecm).so/libsage\1.so/

lib(gap|ecm).so already exists and confuses autotools

RECHECK: module_list
python-sage. automake bug workaround

there's an automake bug [1] that confuses .pyx->.c and .pyx->.cc rules.
the workaround is creating all Makefiles one by one from autogen.sh.
recreated Makefile.am's are fine.

the bug has been fixed upstream, this workaround can be removed
- once the fixed autotools has been released or
- after switching to sane file extensions.

[1] http://debbugs.gnu.org/cgi/bugreport.cgi?bug=14441
python-sage: build system

- header checks
  - cliquer/cl.h
  - flint
  - libgap
- create dependency dummies for cython
- AC_AUTO_HEADER (reduce cruft in gcc-calls)
- checks
  - jinja2
  - whether cython supports dependencies
  - cliquer/cliquer.h
- as_ac_expand
python-sage: Makefiles
python-sage: module-list

- m4ri extra_compile_args
python-sage: use m4ri pkgconfig
python-sage: cythoninit for autogenerated modules

don't know if this is really necessary
python-sage gen_interpreters.py