debuginstall: strip double quotes from editorbin on Windows

The unconditional posix style shlex.split() prior to 94a1ff16f362 handled this.
This isn't mutually exclusive with stripping the quotes in util.findexe()- if
the editor can't be found, this command prints out the string, inside single
quotes.

mercurial/debugcommands.py

@@ -1241,6 +1241,8 b' def debuginstall(ui, **opts):'
     editor = ui.geteditor()
     editor = util.expandpath(editor)
     editorbin = pycompat.shlexsplit(editor, posix=not pycompat.iswindows)[0]
+    if pycompat.iswindows and editorbin[0] == '"' and editorbin[-1] == '"':
+        editorbin = editorbin[1:-1]
     fm.write('editor', _("checking commit editor... (%s)\n"), editorbin)
     cmdpath = util.findexe(editorbin)
     fm.condwrite(not cmdpath and editor == 'vi', 'vinotfound',