add MSDOSSessionLexer and PowerShellSessionLexer.
1. fix wrong versionadded.
Merged birkenfeld/pygments-main into default
Add the lexer for IETF 7405 ABNF <http://www.ietf.org/rfc/rfc7405.txt>.
Add the lexer for traditional `bc: an arbitrary precision calculator language'.
remake _mapping.py.
* Add lexer for `pkg-config <http://www.freedesktop.org/wiki/Software/pkg-config/>`_
See `#1164 <https://bitbucket.org/birkenfeld/pygments-main/issues/1164/linter-to-check-for-single-character#comment-23138389>`_.