Fix chktex columns
Add function to fold include error levels
[Fix #451] Fix include error levels in gcc/clang

Properly compute the level of errors on included files from the actual
errors within the corresponding include in gcc/clang.  OTOH, don't fold
the messages of the errors within the include into the error on the
include, because that's overly verbose [#521]
Remove function to fold include error messages
Fix test case

Regression from 4d40bc7
Fix wording

[ci skip]
Remove outdated comment

[ci skip]
Merge branch '451-fix-include-error-levels'

* 451-fix-include-error-levels:
  Remove function to fold include error messages
  [Fix #451] Fix include error levels in gcc/clang
  Add function to fold include error levels
Update changelog and texinfo manual [#451]
First try att dscanner
Use both --syntaxCheck and --styleCheck instead of -s
Remove --styleCheck. Both arguments are not supported.
Add d-dscanner-syntax and d-dscanner-style
Add d-dscanner-style to flycheck-checkers
Defined :next-checkers to d-dmd
Add URL ref for DScanner checkers
Correct use of :next-checkers for D checkers
Always use d-dscanner-style after d-dscanner-syntax because dscanner --syntaxCheck may give false positives
Call d-dscanner-syntax also when d-dmd emits warnings
Use both d-dscanner-syntax and d-dscanner-syntax as :next-checkers for d-dmd