updated gap & libgap to 4.5.6
moved gap_packages to new build system, deleted braid package
provide a spkg-check to run the libgap testsuite
checked in the build scripts for the database_gap spkg
fix typo in version number
trac #15482: Say very loud that LP variables are positive by default
trac #15482: addressing the reviewer's comments
trac #15482: Scream where I had not thought of screaming before
trac #15482: shortening a line
trac #15482: positive -> non-negative
trac #15482: a broken doctest
trac #15482: rebase on 5.13.rc0
fix output of enumerate_totallyreal_*

The output of enumerate_totallyreal_fields_prim,
enumerate_totallyreal_fields_all, and enumerate_totallyreal_fields_rel
are in general simply the output of Pari. They should belong to
Sage proper, so that the output can be later used right away.

This patch makes sure that the output of integers are Integers,
and the output that looks like polynomials belong to PolynomialRing
add more fixes for enumerate_totallyreal_*

Introduce a new keyword return_pari_objects that is set
to True by default so that current usage of these functions
is not affected.

Fix documentation and add doctests to the functions to show
the new behavior if return_pari_objects is set to False
Merge remote-tracking branch 'trac/u/vbraun/gap-4.6.5' into gap_4_7_2

Conflicts:
	build/pkgs/gap/checksums.ini
	build/pkgs/libgap/checksums.ini
update to gap-4.7.2
upstream merged Jeroens cflags patch
Removed kschur.py
udpate to libgap-4.7.2
Updated checksum for libgap spkg.