glsl: Add front-end support for GLSL 1.30's roundEven built-in.

Implemented using the op-code introduced in the previous commit.

src/glsl/builtins/ir/roundEven

@@ -0,0 +1,21 @@
+((function roundEven
+   (signature float
+     (parameters
+       (declare (in) float arg0))
+     ((return (expression float round_even (var_ref arg0)))))
+
+   (signature vec2
+     (parameters
+       (declare (in) vec2 arg0))
+     ((return (expression vec2 round_even (var_ref arg0)))))
+
+   (signature vec3
+     (parameters
+       (declare (in) vec3 arg0))
+     ((return (expression vec3 round_even (var_ref arg0)))))
+
+   (signature vec4
+     (parameters
+       (declare (in) vec4 arg0))
+     ((return (expression vec4 round_even (var_ref arg0)))))
+))

src/glsl/builtins/profiles/130.frag

@@ -148,6 +148,11 @@ vec2  trunc(vec2  x);
 vec3  trunc(vec3  x);
 vec4  trunc(vec4  x);
 
+float roundEven(float x);
+vec2  roundEven(vec2  x);
+vec3  roundEven(vec3  x);
+vec4  roundEven(vec4  x);
+
 float ceil(float x);
 vec2  ceil(vec2  x);
 vec3  ceil(vec3  x);

src/glsl/builtins/profiles/130.vert

@@ -148,6 +148,11 @@ vec2  trunc(vec2  x);
 vec3  trunc(vec3  x);
 vec4  trunc(vec4  x);
 
+float roundEven(float x);
+vec2  roundEven(vec2  x);
+vec3  roundEven(vec3  x);
+vec4  roundEven(vec4  x);
+
 float ceil(float x);
 vec2  ceil(vec2  x);
 vec3  ceil(vec3  x);