Declare precision also in vertex shaders in GLES renderer.

Some drivers complain that it was declared only in fragment shaders.

data/shaders/pass_gles.vert

@@ -1,5 +1,7 @@
 #version 300 es
 
+precision mediump float;
+
 in vec3 Position;
 in vec2 Texcoord;
 out vec2 uv;

src/graphics/shader.cpp

@@ -110,6 +110,10 @@ GLuint ShaderBase::loadShader(const std::string &file, unsigned type)
     //shader compilation fails with some drivers if there is no precision qualifier
     if (type == GL_FRAGMENT_SHADER)
         code << "precision mediump float;\n";
+#if defined(USE_GLES2)
+    else if (type == GL_VERTEX_SHADER)
+        code << "precision mediump float;\n";
+#endif
 
     code << getHeader();