added offline error handling for rules
impemented rule %= operator
Merge branch 'develop' of https://github.com/boostorg/spirit into feature/x3_keywords
Ported calc5 to X3 (Same as Calc4, this time, we'll incorporate debugging support, plus error handling and reporting).
fixes #5872
wrong underscore crept in
added on_sucess handler (complements on_error)
use enum class for error_handler_result
action should be in core, not auxilary
added x3::ast and x3::forward_ast (specialized versions of boost::variant and boost::recursive_wrapper)
improved variant interface
variant should be named variant. nothing else.
date changes
ported calc6 to x3
Updated tests to catch bug in tst_map
Fixed iterator rollback bug in tst_map
Fixed qi::alternative test code.
Merge pull request #11 from vtnerd/bugfix/tst_map

Bugfix/tst map
Added the seek keyword from spirit v2 repository to x3 extensions.

This patch does not test semantic actions with the seek parser - the
feature is not yet implemented/finalized in x3. All other tests from v2
have been moved.
Added semantic action test to x3 seek parser

The previous commit incorrectly stated that actions were not implemented
in x3, which was untrue.