move src/bin/sage-spkg.in -> sagedist/bin/sage-spkg (#14807)

src/bin might not be accessible before sagelib has been
unpacked/configure/staged/installed. the old toplevel build system
requires sage-spkg earlier.
provide sage-env for sagedist. temporary workaround for sagelib (#14807)
autotools: spkg (#15123)

- missing file (Makefile.build)
- fix paths
- patch idempotence
- sha1 checksum
- package-version (20121217)
- rm .hgignore
Merge branch 'autotools' into sagelib

(autotools are required to build sagelib from git)
chmod +x sage-dist-{install,make} (#14804)
Merge branch 'sagedist' into slb

(autotools are required to build sagelib from git)
build autotools from old build system (#14807)
add autogen rule for core modules (#14807)

autogen creates configure. this is necessary, when building from git.
sage aclocal does not properly locate pkg.m4.

just put it there, resolve later (easier with toplevel configure).
pass correct options to core modules (#14807)
environment workarounds (#14807)

- still require src/bin/sage-env for old build system
- need SAGE_PREFIX for newer packages (sage-env, build/install)
libm4rie: provide pkgconfig file

it's much easier to locate headers the way it works with m4ri.
increase patchlevel by one, as there is no revision field.
Merge branch 'm4rie' into sagelib

need pkgconfig from updated m4rie package
make python-sage accessible from build/install

this is still required to stage conway_polynomials.
python-sage build depends on databases (#14807)

configure needs to set the paths accordingly.
Merge branch 'sagelib' into toplevel

Conflicts:
	build/deps (deleted)
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)