glsl: Add ir_function_signature::is_intrinsic() method

This necessetated renaming the is_intrinsic field to _is_intrinsic.  The
next commit will remove the field.

   text	   data	    bss	    dec	    hex	filename
6036507	 283160	  28608	6348275	 60ddf3	lib64/i965_dri.so before
6036491	 283160	  28608	6348259	 60dde3	lib64/i965_dri.so after

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Acked-by: Ilia Mirkin <imirkin@alum.mit.edu>

src/compiler/glsl/ir.h

@@ -1187,11 +1187,17 @@ public:
    /** Whether or not this function signature is a built-in. */
    bool is_builtin() const;
 
+   /** Whehter or not this function signautre is an intrinsic. */
+   inline bool is_intrinsic() const
+   {
+      return _is_intrinsic;
+   }
+
    /**
     * Whether or not this function is an intrinsic to be implemented
     * by the driver.
     */
-   bool is_intrinsic;
+   bool _is_intrinsic;
 
    /** Indentifier for this intrinsic. */
    enum ir_intrinsic_id intrinsic_id;