Move additional keywords to a flag, revert the removal of 'include'

syntax/ansible.vim

@@ -78,9 +78,15 @@ endif
 syn keyword ansible_debug_keywords debug containedin=yamlBlockMappingKey contained
 highlight link ansible_debug_keywords Debug
 
+if exists("g:ansible_extra_keywords_highlight")
+  syn keyword ansible_extra_special_keywords register always_run changed_when failed_when no_log args vars delegate_to ignore_errors containedin=yamlBlockMappingKey contained
+  highlight link ansible_extra_special_keywords Statement
+endif
+
+syn keyword ansible_special_keywords include until retries delay when only_if become become_user block rescue always notify containedin=yamlBlockMappingKey contained
+highlight link ansible_special_keywords Statement
+
 syn match ansible_with_keywords "\vwith_.+" containedin=yamlBlockMappingKey contained
-syn keyword ansible_special_keywords until retries delay when only_if become become_user block rescue always notify register always_run changed_when failed_when no_log args vars delegate_to ignore_errors containedin=yamlBlockMappingKey contained
 highlight link ansible_with_keywords Statement
-highlight link ansible_special_keywords Statement
 
 let b:current_syntax = "ansible"