Add serveral tests for a==b==c style invalid equality operator uses

invalid-equality-04.vert reproduces Mesa bugzilla #33303.

tests/spec/glsl-1.10/compiler/expressions/invalid-equality-01.vert

+// [config]
+// expect_result: fail
+// glsl_version: 1.10
+// [end config]
+
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+attribute vec4 vertex;
+uniform int a;
+uniform int b;
+uniform int c;
+
+void main() {
+	if (a == b == c) {
+		gl_Position = vertex;
+	} else {
+		gl_Position = vec4(1.0) - vertex;
+	}
+}

tests/spec/glsl-1.10/compiler/expressions/invalid-equality-02.vert

+// [config]
+// expect_result: fail
+// glsl_version: 1.10
+// [end config]
+
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+attribute vec4 vertex;
+
+void main() {
+	if (0 == 1 == 2) {
+		gl_Position = vertex;
+	} else {
+		gl_Position = vec4(1.0) - vertex;
+	}
+}

tests/spec/glsl-1.10/compiler/expressions/invalid-equality-03.vert

+// [config]
+// expect_result: fail
+// glsl_version: 1.10
+// [end config]
+
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+attribute vec4 vertex;
+uniform int a;
+uniform int b;
+uniform int c;
+
+vec4 A(bool flag) {
+	if (flag)
+		return vertex;
+	else
+		return vec4(1.0) - vertex;
+}
+
+void main() {
+	gl_Position = A(a == b == c);
+}

tests/spec/glsl-1.10/compiler/expressions/invalid-equality-04.vert

+// [config]
+// expect_result: fail
+// glsl_version: 1.10
+// [end config]
+
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+attribute vec4 vertex;
+
+vec4 A(bool flag) {
+	if (flag)
+		return vertex;
+	else
+		return vec4(1.0) - vertex;
+}
+
+void main() {
+	gl_Position = A(0 == 1 == 2);
+}