pcbnew: undo last step in interactive routing

[Eldar Khayrullin]

It will be usefull if one can Undo last step in interactive routing with hotkey (P-Cad uses <Backscape> for undo last step).

Application: kicad
Version: 4.1.0-alpha+201606281446+6952~45~ubuntu16.04.1-product, release build
Libraries: wxWidgets 3.0.2
           libcurl/7.47.0 OpenSSL/1.0.2g zlib/1.2.8 libidn/1.32 librtmp/2.3
Platform: Linux 4.4.0-24-generic x86_64, 64 bit, Little endian, wxGTK
- Build Info -
wxWidgets: 3.0.2 (wchar_t,wx containers,compatible with 2.8)
Boost: 1.58.0
Curl: 7.47.0
KiCad - Compiler: GCC 5.3.1 with C++ ABI 1009
        Settings: USE_WX_GRAPHICS_CONTEXT=OFF
                  USE_WX_OVERLAY=OFF
                  KICAD_SCRIPTING=ON
                  KICAD_SCRIPTING_MODULES=ON
                  KICAD_SCRIPTING_WXPYTHON=ON
                  USE_FP_LIB_TABLE=HARD_CODED_ON
                  BUILD_GITHUB_PLUGIN=ON

[John Beard (john-j-beard)]

Adding missing-gal-tool as this is possible in legacy mode.

Also, this is related to lp:1448460 as that is essentially the same function, but with all segments at once.

[Seth Hillbrand (sethh)]

@Jeff- This is the undo last step command action that is missing. Art's bug is about deleting tracks while routing which just need the delete key.

[Jeff Young (jeyjey)]

@Seth, as I understand it the backspace key used to undo the last step, while the delete key deleted the entire track. (I think both now delete the entire track.)

[Seth Hillbrand (sethh)]

The undo command existed in legacy but never was ported to GAL. This is one of the last missing GAL tools.

The hotkey assigned to it is secondary to the missing functionality (which is the focus of this bug).

[KiCad Janitor (kicad-janitor)]

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/2028