Define-out precision qualifiers in test shaders for GLSL 1.20.

Causes the errors to abort on AMD cards.

src/Magnum/Test/AbstractShaderProgramGLTestFiles/MyShader.frag

@@ -1,3 +1,7 @@
+#if !defined(GL_ES) && __VERSION__ == 120
+#define lowp
+#endif
+
 uniform lowp float multiplier;
 uniform lowp vec4 color;
 uniform lowp vec4 additions[3];

src/Magnum/Test/AbstractShaderProgramGLTestFiles/MyShader.vert

@@ -1,3 +1,7 @@
+#if !defined(GL_ES) && __VERSION__ == 120
+#define mediump
+#endif
+
 attribute mediump vec4 position;
 
 uniform mediump mat4 matrix;

src/Magnum/Test/MeshGLTest.cpp

@@ -396,6 +396,9 @@ FloatShader::FloatShader(const std::string& type, const std::string& conversion)
 
     vert.addSource(
         #if !defined(MAGNUM_TARGET_GLES) || defined(MAGNUM_TARGET_GLES2)
+        "#if !defined(GL_ES) && __VERSION__ == 120\n"
+        "#define mediump\n"
+        "#endif\n"
         "attribute mediump " + type + " value;\n"
         "varying mediump " + type + " valueInterpolated;\n"
         #else
@@ -408,7 +411,10 @@ FloatShader::FloatShader(const std::string& type, const std::string& conversion)
         "}\n");
 
     #if !defined(MAGNUM_TARGET_GLES) || defined(MAGNUM_TARGET_GLES2)
-    frag.addSource("varying mediump " + type + " valueInterpolated;\n"
+    frag.addSource("#if !defined(GL_ES) && __VERSION__ == 120\n"
+                   "#define mediump\n"
+                   "#endif\n"
+                   "varying mediump " + type + " valueInterpolated;\n"
                    "void main() { gl_FragColor = " + conversion + "; }\n");
     #else
     frag.addSource("in mediump " + type + " valueInterpolated;\n"
@@ -1141,7 +1147,10 @@ MultipleShader::MultipleShader() {
     Shader frag(Version::GLES200, Shader::Type::Fragment);
     #endif
 
-    vert.addSource("attribute mediump vec4 position;\n"
+    vert.addSource("#if !defined(GL_ES) && __VERSION__ == 120\n"
+                   "#define mediump\n"
+                   "#endif\n"
+                   "attribute mediump vec4 position;\n"
                    "attribute mediump vec3 normal;\n"
                    "attribute mediump vec2 textureCoordinates;\n"
                    "varying mediump vec4 valueInterpolated;\n"

src/Magnum/Test/PrimitiveQueryGLTest.cpp

@@ -102,6 +102,9 @@ void PrimitiveQueryGLTest::primitivesGenerated() {
             Shader vert(Version::GL210, Shader::Type::Vertex);
 
             CORRADE_INTERNAL_ASSERT_OUTPUT(vert.addSource(
+                "#if !defined(GL_ES) && __VERSION__ == 120\n"
+                "#define lowp\n"
+                "#endif\n"
                 "attribute lowp vec4 position;\n"
                 "void main() {\n"
                 "    gl_Position = position;\n"

src/Magnum/Test/SampleQueryGLTest.cpp

@@ -119,6 +119,9 @@ MyShader::MyShader() {
     #endif
 
     vert.addSource(
+        "#if !defined(GL_ES) && __VERSION__ == 120\n"
+        "#define lowp\n"
+        "#endif\n"
         "attribute lowp vec4 position;\n"
         "void main() {\n"
         "    gl_Position = position;\n"