GAL: Zoom and grid selection not updated correctly in context menu

[Ben Kempke]

After changing the grid size or zoom level in GAL mode, the change is not reflected in the corresponding sub-menu. In order for the correct selection to appear, you must refresh the context menu by closing and re-opening.

Application: kicad
Version: (2015-07-28 BZR 6012, Git 63b0e63)-product debug build
wxWidgets: Version 3.0.2 (debug,wchar_t,compiler with C++ ABI 1002,GCC 4.9.2,wx containers,compatible with 2.8)
Platform: Linux 3.19.0-22-generic x86_64, 64 bit, Little endian, wxGTK
Boost version: 1.54.0
         USE_WX_GRAPHICS_CONTEXT=OFF
         USE_WX_OVERLAY=OFF
         KICAD_SCRIPTING=OFF
         KICAD_SCRIPTING_MODULES=OFF
         KICAD_SCRIPTING_WXPYTHON=OFF
         USE_FP_LIB_TABLE=HARD_CODED_ON
         BUILD_GITHUB_PLUGIN=ON