keysymdef.h: Fix the documented perl regexp

+ is interpreted when not escaped.
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

include/X11/keysymdef.h

@@ -86,8 +86,8 @@ SOFTWARE.
  * Mnemonic names for keysyms are defined in this file with lines
  * that match one of these Perl regular expressions:
  *
- *    /^\#define XK_([a-zA-Z_0-9]+)\s+0x([0-9a-f]+)\s*\/\* U+([0-9A-F]{4,6}) (.*) \*\/\s*$/
- *    /^\#define XK_([a-zA-Z_0-9]+)\s+0x([0-9a-f]+)\s*\/\*\(U+([0-9A-F]{4,6}) (.*)\)\*\/\s*$/
+ *    /^\#define XK_([a-zA-Z_0-9]+)\s+0x([0-9a-f]+)\s*\/\* U\+([0-9A-F]{4,6}) (.*) \*\/\s*$/
+ *    /^\#define XK_([a-zA-Z_0-9]+)\s+0x([0-9a-f]+)\s*\/\*\(U\+([0-9A-F]{4,6}) (.*)\)\*\/\s*$/
  *    /^\#define XK_([a-zA-Z_0-9]+)\s+0x([0-9a-f]+)\s*(\/\*\s*(.*)\s*\*\/)?\s*$/
  *
  * Before adding new keysyms, please do consider the following: In