OClint: fix parsing.
OClint: slightly more robust regexps.
Add new clang-tidy and clang-check checkers

These checkers use an existing compilation database so that the actual
flags used in the compile are used in the check.
Fix bad variable initialization

Previously, non-core users could not use ocamlc as their syntax checker because this check would reset the wrong variable. 
Setting g:syntastic_ocaml_use_ocamlc without core now works as intended.
Merge pull request #1161 from dtwitty/patch-1

camlp4o: fix bad variable initialization.
Allow oclint to use cmake compilation databases.
Merge remote-tracking branch 'bbanier/t/clang_tools' into clang_tools
Clang tools: work without a compilation database.  Cleanup.
Clang tools: missing space.
Clang tools: check exit codes.
A cleaner way to kill default variables.
Merge commit '8e229e41a308f349cad2f17386df91f7f357f0b6'