(ada-create-syntax-table): Move

(ada-create-syntax-table): Move
set-syntax-table from here to ...
(ada-mode): ... here.  Do not change global value of
comment-multi-line.  Call new function
ada-initialize-syntax-table-properties and add new function
ada-handle-syntax-table-properties to font-lock-mode-hook.
(ada-deactivate-properties, ada-initialize-properties): Replace
by new functions ...
(ada-handle-syntax-table-properties)
(ada-initialize-syntax-table-properties)
(ada-set-syntax-table-properties): ... to set up syntax-table
properties uniformly, independently from whether font-lock-mode
is enabled or not.  Handle read-only buffers and do not change
undo-list when setting syntax-table properties.
(ada-after-change-function): Use ada-set-syntax-table-properties.