c: allow using clang to check C.

Since clang as a interface compatible with gcc's, use the gcc backend for
both.

Signed-off-by: Florent Bruneau <florent.bruneau@intersec.com>
c/c++: add an option to ignore default include dirs.

Signed-off-by: Florent Bruneau <florent.bruneau@intersec.com>
c/c++: force language in compiler invocation.

That way, the files are properly treated as C/C++ even when they don't
have the standard file extension

Signed-off-by: Florent Bruneau <florent.bruneau@intersec.com>
add syntastic#util#ParseMagicNumber()

this will (hopefully) be used in the perl checker to fix #422
Merge pull request #425 from Fruneau/c-cpp-improvements

C/C++ improvements: clang support and default include exclusion
perl: add -Tc to makeprg if the shebang contains -T

If the shebang contains -T, then the makeprg looks like:
    perl '/path/to/efm_perl.pl' -c -w '/tmp/foo.pl' -Tc

Mods to syntastic#util#ParseMagicNumber
 * rename it to ParseShebang (since this name seems more common)
 * return an empty result set rather than 0 so callers dont have to
   check if empty()
added config file support for javac checker and windows os support
javac checker path seperator related bugfix added
Merge pull request #426 from troydm/master

javac checker related bugs fixed and config file functionality added
javac quotes changed to fnameescape
efm_perl: fix warning about uninitialized $opt_I

$ perl syntax_checkers/efm_perl.pl -c -w /dev/null
Use of uninitialized value $opt_I in split at syntax_checkers/efm_perl.pl line 94.
efm_perl: add support for checking - (stdin)

In simple case it just miss warnings:
  $ echo '$a=5;' | perl syntax_checkers/efm_perl.pl -c -w -
  (nothing, while it should be this:)
  W:-:1:Name "main::a" used only once: possible typo
In complex cases with some other errors it show crazy warnings
in crazy line numbers.
Use case when efm_perl run on STDIN can be found in issue#261.
add support dart
Ignore tidy warning about "search" value for <input> type attribute
Merge pull request #432 from tomjakubowski/master

Ignore tidy warning about <input> tags with type="search"
Merge pull request #430 from maksimr/master

Added Dart support
Merge pull request #427 from troydm/master

javac checker quotes changed to fnameescape
Merge pull request #428 from powerman/efm_perl

Efm perl: few fixed
add a makeprg builder

The problem
---

Some people want to change the syntax checker args and/or executable.
Currently they have to create their own checker to do this.

Solution
---

Create a standard API for building a makeprg that allows users to set
global variables to override the exe or args.

This API is in use in the coffee and python/flake8 checkers - as
proofs of concept.

So, if the user wanted to change the args that get passed to `flake8`
they can now set `let g:syntastic_python_flake8_args="--foo --bar"` in
their vimrc. Similarly they could set `let
g:syntastic_python_flake8_exe='python foo.py'`
Merge https://github.com/scrooloose/syntastic