Fix compilation on arm systems.

Also disabled the whole questionable GL memory test for non-debug builds.

src/StelMainView.cpp

@@ -1431,16 +1431,20 @@ void StelMainView::doScreenshot(void)
 		{
 			context->functions()->initializeOpenGLFunctions();
 			//qDebug() << "initializeOpenGLFunctions()...";
-#ifndef Q_OS_MAC
+			// TODO: Investigate this further when GL memory issues should appear.
 			// Make sure we have enough free GPU memory!
+#ifndef NDEBUG
+#ifdef GL_GPU_MEMORY_INFO_CURRENT_AVAILABLE_VIDMEM_NVX
 			GLint freeGLmemory;
 			context->functions()->glGetIntegerv(GL_GPU_MEMORY_INFO_CURRENT_AVAILABLE_VIDMEM_NVX, &freeGLmemory);
 			qCDebug(mainview)<<"Free GPU memory:" << freeGLmemory << "kB -- we ask for " << customScreenshotWidth*customScreenshotHeight*8 / 1024 <<"kB";
+#endif
+#ifdef GL_RENDERBUFFER_FREE_MEMORY_ATI
 			GLint freeGLmemoryAMD[4];
 			context->functions()->glGetIntegerv(GL_RENDERBUFFER_FREE_MEMORY_ATI, freeGLmemoryAMD);
 			qCDebug(mainview)<<"Free GPU memory (AMD version):" << (uint)freeGLmemoryAMD[1]/1024 << "+" << (uint)freeGLmemoryAMD[3]/1024 << " of " << (uint)freeGLmemoryAMD[0]/1024 << "+" << (uint)freeGLmemoryAMD[2]/1024 << "kB -- we ask for " << customScreenshotWidth*customScreenshotHeight*8 / 1024 <<"kB";
 #endif
-
+#endif
 			GLint texSize,viewportSize[2],rbSize;
 			context->functions()->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &texSize);
 			context->functions()->glGetIntegerv(GL_MAX_VIEWPORT_DIMS, viewportSize);