Remove spacemacs/add-to-local-vars-hook and use (format ...)

It is better to directly hook function using the conventional hook
functions.

Replace usage of (concat ...) by a (format ...) from which is more
readable.

layers/+distributions/spacemacs-base/funcs.el

@@ -51,13 +51,7 @@
 
 (defun spacemacs//run-local-vars-mode-hook ()
   "Run a hook for the major-mode after the local variables have been processed."
-  (run-hooks (intern (concat (symbol-name major-mode) "-local-vars-hook"))))
-
-;; http://stackoverflow.com/a/5148435/3086454
-(defun spacemacs/add-to-local-vars-hook (mode func)
-  "Add hook to mode--local-vars-hook which is executed after the
-local variables have been processed."
-  (add-hook (intern (concat (symbol-name mode) "-local-vars-hook")) func))
+  (run-hooks (intern (format "%S-local-vars-hook" major-mode))))
 
 (defun spacemacs/echo (msg &rest args)
   "Display MSG in echo-area without logging it in *Messages* buffer."

layers/+lang/elixir/packages.el

@@ -124,8 +124,8 @@
                    (cons 'elixir-enable-compilation-checking nil))
       (add-to-list 'safe-local-variable-values
                    (cons 'elixir-enable-compilation-checking t))
-      (spacemacs/add-to-local-vars-hook 'elixir-mode
-                                        'spacemacs//elixir-enable-compilation-checking))))
+      (add-hook 'elixir-mode-local-vars-hook
+                'spacemacs//elixir-enable-compilation-checking))))
 
 (defun elixir/init-elixir-mode ()
   (use-package elixir-mode

layers/+lang/haskell/packages.el

@@ -106,7 +106,8 @@
     :defer t
     :init
     (progn
-      (spacemacs/add-to-local-vars-hook 'haskell-mode #'spacemacs-haskell//setup-completion-backend)
+      (add-hook 'haskell-mode-local-vars-hook
+                #'spacemacs-haskell//setup-completion-backend)
 
       (defun spacemacs//force-haskell-mode-loading ()
         "Force `haskell-mode' loading when visiting cabal file."

layers/+lang/ruby/packages.el

@@ -125,8 +125,9 @@
     :defer t
     :init
     (progn
-      (spacemacs/add-to-local-vars-hook 'ruby-mode 'spacemacs//ruby-enable-rspec-mode)
-      (spacemacs/add-to-local-vars-hook 'enh-ruby-mode 'spacemacs//ruby-enable-rspec-mode)
+      (spacemacs/add-to-hooks 'spacemacs//ruby-enable-rspec-mode
+                              '(ruby-mode-local-vars-hook
+                                enh-ruby-mode-local-vars-hook))
       ;; remove hooks automatically added by rspec via autoload
       ;; because we want to be able to control when rspec-mode is
       ;; loaded based on the layer variable `ruby-test-runner'
@@ -195,9 +196,9 @@
   "Define keybindings for ruby test mode"
   (use-package ruby-test-mode)
     :defer t
-    :init
-    (spacemacs/add-to-local-vars-hook 'ruby-mode 'spacemacs//ruby-enable-ruby-test-mode)
-    (spacemacs/add-to-local-vars-hook 'enh-ruby-mode 'spacemacs//ruby-enable-ruby-test-mode)
+    :init (spacemacs/add-to-hooks 'spacemacs//ruby-enable-ruby-test-mode
+                                  '(ruby-mode-local-vars-hook
+                                    enh-ruby-mode-local-vars-hook))
     :config
     (progn
       ;; `ruby-test-mode' adds a hook to enable itself, this hack