Drop support for ancient Pango versions

Now that GTK+ 3 and wxWidgets >= 3.2 are required, it's safe to say that
an ancient Pango version older than 1.38 (released 10 years ago) is not
being used.

Author: vslavik

src/colorscheme.cpp

@@ -28,15 +28,6 @@
 #include <wx/artprov.h>
 #include <wx/settings.h>
 
-#ifdef __WXGTK__
-    #include <pango/pango.h>
-    #if PANGO_VERSION_CHECK(1,38,0)
-        #define SUPPORTS_BGALPHA
-    #endif
-#else
-    #define SUPPORTS_BGALPHA
-#endif
-
 
 namespace
 {
@@ -128,10 +119,8 @@ wxColour ColorScheme::DoGet(Color color, Mode mode)
         case Color::ItemContextBgHighlighted:
             #if defined(__WXMSW__)
             return sRGB(255, 255, 255, 0.50);
-            #elif defined(SUPPORTS_BGALPHA)
-            return sRGB(255, 255, 255, 0.35);
             #else
-            return DoGet(Color::ItemContextBg, mode);
+            return sRGB(255, 255, 255, 0.35);
             #endif
 
         // Tags: