GLSpectrum touchscreen updates

Add "show all controls" button, that allows most of the "set once"
controls to be hidden on small screens. Please feel free to make a
better icon! Could also be hidden if !ANDROID, if you don't like it.
Add pinch and pan gestures, for frequency scrolling and zooming in to
spectrum.
Queue frequencies requested by scrolling, so intermediate frequencies
can be omitted, if device is slow to update its frequency.
Support non-integer pixel ratios.
Add popup sliders for dials.
Add DialogPositioner for dialogs.
Add layout to spectrum markers dialog, so that it can be resized, to fit
on smaller screens.

sdrgui/gui/glshaderspectrogram.cpp

@@ -26,6 +26,10 @@
 #include <QVector4D>
 #include <QDebug>
 
+#ifdef ANDROID
+#include <GLES3/gl3.h>
+#endif
+
 #include "gui/glshaderspectrogram.h"
 #include "util/colormap.h"
 
@@ -314,7 +318,7 @@ void GLShaderSpectrogram::initTextureMutable(const QImage& image)
 
     glGenTextures(1, &m_textureId);
     glBindTexture(GL_TEXTURE_2D, m_textureId);
-    glTexImage2D(GL_TEXTURE_2D, 0, GL_RED,
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_R8,
         image.width(), image.height(), 0, GL_RED, GL_UNSIGNED_BYTE, image.constScanLine(0));
 
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);