Fix the errorformat and improve to show only relevant messages

The comments in the previous errorformat broke it. The new error format correctly detects file and line numbers and provides a single entry in the quickfix list for each failure with the full failure message.

Author: reinh

compiler/exunit.vim

@@ -16,15 +16,7 @@ let s:cpo_save = &cpo
 set cpo-=C
 
 CompilerSet makeprg=mix\ test
-
-CompilerSet errorformat=
- \%A\ \ %n)\ %m, " 1) test name (Module)
- \%C,%C,%C,%C, " following 4 lines of failure info
- \%Z\ \ \ \ \ at\ %f:%l, " at foo_test:14
- \%-GFailures%.%#, " ignore three test output summary lines
- \%-GFinished%.%#,
- \%-G%n\ tests%.%#,
- \%-G\\s%# " ignore blank lines
+CompilerSet errorformat=%A\ \ %.)\ %m(%.%#),%C\ \ \ \ \ **%m,%C\ \ \ \ \ \ \ %m,%Z\ \ \ \ \ at\ %f:%l,%-G%.%#
 
 let &cpo = s:cpo_save
 unlet s:cpo_save