Fixes hi-dpi on Windows

- Fixes incorrect install path for icons
- Fixes incorrect font size conversion from "Pango units" (updates some comments)
- Fixes incorrect volume icon in directory browser

CMakeLists.txt

@@ -368,6 +368,8 @@ if(NOT DEFINED ICONSDIR)
         else()
             set(ICONSDIR "${CMAKE_INSTALL_PREFIX}/share/icons")
         endif()
+    else()
+        set(ICONSDIR "${DATADIR}/icons")
     endif()
 endif()