5x speedup to prime_pi
prime_pi: fix off by 1 mallocing issue
remove trailing \'s and other little cleanup
fix doctest
Trac 11475 reviewer patch - very minor prime_pi plot doc improvement
Trac 15018: added recover_formula, recover_formula_internal, prefix_to_infix, and to_infix_internal to logicparser.py
Minor review tweaks.
Merge branch 'develop' into public/ticket/15018

* develop: (467 commits)
  Updated Sage version to 6.1.beta5
  Don't use "missing"
  trac 15265: various changes, finishing review.
  allow disabling of maintainer mode
  trac 15265: Additional change to farey.cpp.
  trac 15265: Minor changes to farey_symbol.pyx
  trac 15265: Minor changes to sl2z.cpp and sl2z.hpp.
  trac 15265: Minor changes to farey.cpp and farey.hpp.
  Run "missing" using bash
  fix tarball url
  trac 15265: Add some further examples and one test to _acton_ of elements of arithmetic groups.
  Source sage-env inside configure
  Improved Karatsuba: more thorough tests
  bootstrap configure: small fixes
  make saving of the confball optional in bootstrap
  fix typos in SPKG.txt
  also commit changes to confball in sage-update-version
  add a SPKG.txt file
  rename to bootstrap, run during version bump
  trac 15265: correct mistakes done while converting to git branch.
  ...
trac 15704: Stupid waste of time in graphs 1
trac #15704: Adding a doctest
trac #15704: Changing add_edge to _backend.add_edge in the (Di)Graph constructor
Merge branch 'develop' into public/ticket/15018

* develop: (120 commits)
  Updated Sage version to 6.1.rc0
  only use CONFVERSION after it has been incremented
  note that the E6->A5 rule is now implemented
  document the glibc bug workaround patch
  Avoid scanf instead of just ignoring rest of file
  bump confball version
  fix for the m4_divert_push error
  sage-clone-source: allow downloading the configure tarball
  Require autoconf 2.64
  revised thematic tutorial regarding maximal_subgroup(s) method
  reference: branching_rules: minor fixup
  bump confball version
  removed bogus commits
  LinearMatroid.is_field_equivalent now tests if self is other before calling LinearMatroid._is_field_isomorphism.
  implemented maximal_subgroup(s) as a WeylCharacterRing method etc.
  Updated Sage version to 6.1.beta6
  Do not use the GNU extension chmod --recursive
  Workaround for glibc-2.18 scanf bug when building ATLAS
  Added  free_group and finitely_presented_group
  Made the repr sorted for the rules.
  ...
fix basis of spaces of modular forms in positive characteristic
trac #16272: Replacing availability by existence and forwarding the results between design constructors
trac #16272: merge #16281

Conflicts:
	src/sage/combinat/designs/bibd.py
	src/sage/combinat/designs/block_design.py
trac #16272: fix doctests
trac #16272: finer doctest to test the output of transversal_design
trac #16272: ultimate doctest
trac #16272: simplifying the structure of orthogonal_array
trac #16272: Merged with updated #16227