Add ebuild-mode

Adds ebuild-mode layer for development of Gentoo ebuilds, as requested
in Github bug syl20bnr#6606

layers/+lang/ebuild/README.org

@@ -0,0 +1,25 @@
+#+TITLE: Ebuild contribution layer for Spacemacs
+
+[[file:img/gentoo.png]]
+
+* Table of Contents                                        :TOC_4_gh:noexport:
+ - [[#description][Description]]
+ - [[#install][Install]]
+ - [[#key-bindings][Key bindings]]
+
+* Description
+This layer supports [[https://gentoo.org][Gentoo]] [[https://devmanual.gentoo.org/ebuild-writing/index.html][ebuild]] and [[https://devmanual.gentoo.org/eclass-writing/index.html][eclass]] development in Spacemacs.
+
+* Install
+To use this configuration layer, add it to your =~/.spacemacs=. You will need to
+add =ebuild= to the existing =dotspacemacs-configuration-layers= list in this
+file.
+
+* Key bindings
+
+| Key Binding | Description            |
+|-------------+------------------------|
+| ~SPC m n~   | Insert skeleton ebuild |
+| ~SPC m k~   | Edit keywords          | 
+| ~SPC m e~   | Run ebuild command     | 
+| ~SPC m a~   | Add ChangeLog entry    |

layers/+lang/ebuild/packages.el

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+;;; packages.el --- ebuild layer packages file for Spacemacs.
+;;
+;; Copyright (c) 2012-2017 Kai Wohlfahrt & Contributors
+;;
+;; Author:  <https://github.com/kwohlfahrt>
+;; URL: https://github.com/syl20bnr/spacemacs
+;;
+;; This file is not part of GNU Emacs.
+;;
+;;; License: GPLv3
+
+(defun ebuild/init-ebuild-mode ()
+  (use-package ebuild-mode
+    :defer t
+    :mode ("\\.\\(ebuild\\|eclass\\)" . ebuild-mode)
+    :init
+    (progn
+      (spacemacs/set-leader-keys-for-major-mode 'ebuild-mode
+        "n" 'ebuild-mode-insert-skeleton
+        "k" 'ebuild-mode-keyword
+        "e" 'ebuild-run-command
+        "a" 'ebuild-run-echangelog))))
+
+(defconst ebuild-packages
+  '((ebuild-mode :location (recipe :fetcher github
+                                   :repo "emacsmirror/ebuild-mode"))))