GIT version doesn't build anymore

Hi,
my last successful build of the GIT version of Balsa was on 2018/07/16

But now I encounter problems.

First, in configure.ac it  checks pkg_config enchant-2  which doesn't  
exist in Gentoo even though enchant-2.1.2 is installed here.
Therefore it checks for  <= enchant-1.6.0 which fails.

Disabling this check in configure.ac it fails lateron with

/usr/include/webkitgtk-4.0/webkit2/WebKitContextMenuItem.h:64:60:  
error: unknown type name 'GtkAction'; did you mean 'AtkAction'?
  webkit_context_menu_item_new                               
(GtkAction              *action);
                                                             ^~~~~~~~~
                                                             AtkAction
/usr/include/webkitgtk-4.0/webkit2/WebKitContextMenuItem.h:85:61:  
error: unknown type name 'GtkAction'
  WEBKIT_DEPRECATED_FOR(webkit_context_menu_item_get_gaction) GtkAction  
*
                                                              ^~~~~~~~~

I have webkit-gtk-2.18.6 installed here. Is the patch for this old  
version removed?
I had no problems with the GIT version of 2018/07/16 with the same  
version of webkit-gtk.

Many thanks for a hint,
Helmut