Comparison of ZZ/nZZ disregards category
Also refine category when calling is_field()
Document the "proof" argument of is_field.
Warn if an integer mod ring is mistakenly found in Fields()
Replace optional "category" argument by "is_field"
Raise an error if a non-prime integer mod ring is found in Fields()
Make pickling of ZZ/nZZ aware of being in Fields()
Merge branch 'master' into ticket/15229

* master: (216 commits)
  also remove untracked directories after an aborted import patch
  trac_interface: encode fields with utf-8 as well
  sage.dev: don't textwrap during doctesting
  patch.py: deal with hg's silly copy commands
  SageDev: fix pull doctest
  SageDev: remove branch keyword from pull
  fix doctest errors in SageDev.push
  remove (now) bad uses of SageDev.pull
  remove unused garbage
  dumb down pull to fix it
  don't abort ticket editing on nop push
  remove last reference to download command
  fix dev scripts in emacs shell
  remove , from my name
  fixed missleading error message for trac authentication error
  [FIXUP] 5.13.beta2: update git specific files
  5.13.beta2
  5.13.beta2
  fixed import statement for the commandline interface
  fix doctest failure from bad merge conflict resolution
  ...
Trac 15229: Complete a phrase in the doc, remove trailing whitespace
Let gf2x use --libdir and make SAGE_FAT_BINARY work.
Replace symlink in a more portable way.
Make generic build of gf2x smarter.
More fixes for gf2x generic build.
Support SSE2 on x86_64 for gf2x.
Simplify generic build of gf2x.
Properly autoreconfed patches.
Document new gf2x patch.
Prevent autotools to regenerate files.
Simplify gf2x patches
Make the SSE2 stuff work if the compiler does not support SSE2.
Implemented marked Cartan types and refactored common code.