Expand implicit argument conversions to also include handling built-in function calls.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@26080 e7fa87d3-cd2b-0410-9028-fcbf551c1848

Test/140.frag

@@ -26,3 +26,9 @@ layout(location=3) in vec4 vl;  // ERROR
 #extension GL_ARB_separate_shader_objects : enable
 
 layout(location=4) in vec4 vl2;
+
+void foo()
+{
+    vec2 r1 = modf(v.xy, v.zw);  // ERROR, v.zw not l-value
+    vec2 r2 = modf(o.xy, o.zw);
+}