Add b:clojure_syntax_without_core_keywords

Some namespaces exclude vars from clojure.core; examples of this are
namespaces that use core.logic or piplin.

This variable allows a plugin to have complete control over all keyword
matches in the buffer.

Author: guns

README.markdown

@@ -116,8 +116,12 @@ to have a certain set of symbols highlighted in a certain way, while the
 buffer-local version is intended for plugin authors who wish to highlight
 symbols dynamically.
 
+If the buffer flag `b:clojure_syntax_without_core_keywords` is set, vars from
+`clojure.core` are not highlighted by default. This is useful for highlighting
+namespaces that have set `(:refer-clojure :only [])`.
+
 [`vim-clojure-highlight`](https://github.com/guns/vim-clojure-highlight) uses
-this feature to highlight extra vars when connected to a REPL.
+these variables to highlight extra vars when connected to a REPL.
 
 Indent Options
 ==============

doc/clojure.txt

@@ -138,6 +138,9 @@ identifiers:
 <
 Refer to the Clojure syntax script for valid syntax group names.
 
+If the |buffer-variable| *b:clojure_syntax_without_core_keywords* is set, only
+language constants and special forms are matched.
+
 Setting *g:clojure_fold* enables folding Clojure code via the syntax engine.
 Any list, vector, or map that extends over more than one line can be folded
 using the standard Vim |fold-commands|.

syntax/clojure.vim

@@ -41,7 +41,14 @@ function! s:syntax_keyword(dict)
 	endfor
 endfunction
 
-call s:syntax_keyword(s:clojure_syntax_keywords)
+if exists('b:clojure_syntax_without_core_keywords') && b:clojure_syntax_without_core_keywords
+	" Only match language specials and primitives
+	for s:key in ['clojureBoolean', 'clojureConstant', 'clojureException', 'clojureSpecial']
+		execute 'syntax keyword' s:key join(s:clojure_syntax_keywords[s:key], ' ')
+	endfor
+else
+	call s:syntax_keyword(s:clojure_syntax_keywords)
+endif
 
 if exists('g:clojure_syntax_keywords')
 	call s:syntax_keyword(g:clojure_syntax_keywords)
@@ -51,6 +58,7 @@ if exists('b:clojure_syntax_keywords')
 	call s:syntax_keyword(b:clojure_syntax_keywords)
 endif
 
+unlet! s:key
 delfunction s:syntax_keyword
 
 " Keywords are symbols: