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()

autoload/syntastic/util.vim

@@ -23,7 +23,7 @@ endfunction
 "returns
 "
 "{'exe': '/usr/bin/perl', 'args': ['-f', '-bar']}
-function! syntastic#util#ParseMagicNumber()
+function! syntastic#util#ParseShebang()
     for lnum in range(1,5)
         let line = getline(lnum)
 
@@ -33,6 +33,8 @@ function! syntastic#util#ParseMagicNumber()
             return {'exe': exe, 'args': args}
         endif
     endfor
+
+    return {'exe': '', 'args': []}
 endfunction
 
 let &cpo = s:save_cpo

syntax_checkers/perl.vim

@@ -40,7 +40,18 @@ function! SyntaxCheckers_perl_GetLocList()
     else
         let makeprg = g:syntastic_perl_efm_program . ' ' . shellescape(expand('%'))
     endif
+    let makeprg .= s:ExtraMakeprgArgs()
+
     let errorformat =  '%t:%f:%l:%m'
 
     return SyntasticMake({ 'makeprg': makeprg, 'errorformat': errorformat })
 endfunction
+
+function! s:ExtraMakeprgArgs()
+    let shebang = syntastic#util#ParseShebang()
+    if index(shebang['args'], '-T') != -1
+        return ' -Tc'
+    endif
+
+    return ''
+endfunction