add a simple debug message system

We may want to add debug messages at many points. We can add them as we
find we need them - i.e. when debugging stuff with users.

autoload/syntastic/util.vim

@@ -92,6 +92,16 @@ function! syntastic#util#wideMsg(msg)
     let &showcmd=old_showcmd
 endfunction
 
+if !exists("g:syntastic_debug")
+    let g:syntastic_debug = 0
+endif
+
+function! syntastic#util#debug(msg)
+    if g:syntastic_debug
+        echomsg "(Syntastic debug) - " . a:msg
+    endif
+endfunction
+
 let &cpo = s:save_cpo
 unlet s:save_cpo
 " vim: set et sts=4 sw=4:

plugin/syntastic.vim

@@ -132,6 +132,8 @@ function! s:CacheErrors(...)
             endif
 
             for checker in checkers
+                call syntastic#util#debug("CacheErrors: Invoking checker: " . checker.name())
+
                 let loclist = checker.getLocList()
 
                 if !loclist.isEmpty()
@@ -257,6 +259,8 @@ endfunction
 "   'defaults' - a dict containing default values for the returned errors
 "   'subtype' - all errors will be assigned the given subtype
 function! SyntasticMake(options)
+    call syntastic#util#debug('SyntasticMake: called with options: '. string(a:options))
+
     let old_loclist = getloclist(0)
     let old_makeprg = &l:makeprg
     let old_shellpipe = &shellpipe