Trac #15505: Add missing relations to braid group
Trac #15488: Fix misplaced sig_on() statements inside try
Trac #15422: Fix p-adic factorizations for non-squarefree polynomials
Trac #15433: OS X's accelerate framework no longer pretends to be atlas
Trac #15301: fix a link to the PDF version of PREP tutorials
Trac #15007: Alias .diff() and .differentiate() to .derivative() in
polynomial rings
Trac #11934: Add a doctest to confirm that full_simplify() doesn't affect the imaginary part of an expression.
Trac #15392: support for minimal models of projective maps
Trac #13352: Use mpn_popcount() for bitset_len(), clean up bitset interface
Trac #10093: Clean up documentation of sage/misc/bitset.pyx
Trac #10093: Raise ValueError when trying to init a Bitset with capacity 0
Trac #15150: Implemented NCSym.
Trac 15433: work around for incompatibility between g++ and an OS X header
Trac #15433: don't build sqlite on OS X 10.9
Trac #15433: define __ACCELERATE__ on OS X
5.13.rc0
5.13.rc0
Merge 'sage-5.13.rc0'
Merge branch 'upstream' into build_system
[FIXUP] 5.13.rc0: update git specific files

These currently include
 * VERSION.txt
 * package-version.txt
 * checksums.ini