Fixed nested comments

Comments can now be nested.

acs.vim

@@ -21,7 +21,7 @@ hi def link TODO Todo
 " @Spell means spell checking if I understand correctly.
 syn region line_comment start="//" end="$" contains=TODO,@Spell
 hi def link line_comment Comment
-syn region block_comment start="/\*" end="\*/" contains=TODO,@Spell
+syn region block_comment start="/\*" end="\*/" contains=TODO,@Spell,line_comment,block_comment
 hi def link block_comment Comment
 
 syn region string start=+"+ end=+"+