ENH: Add While support

Docs/cmake-indent.vim

@@ -65,8 +65,8 @@ fun! CMakeGetIndent(lnum)
                     \            ')\s*' .
                     \            '\(' . cmake_regex_comment . '\)\?$'
 
-  let cmake_indent_begin_regex = '^\s*\(IF\|MACRO\|FOREACH\|ELSE\)\s*('
-  let cmake_indent_end_regex = '^\s*\(ENDIF\|ENDFOREACH\|ENDMACRO\|ELSE\)\s*('
+  let cmake_indent_begin_regex = '^\s*\(IF\|MACRO\|FOREACH\|ELSE\|WHILE\)\s*('
+  let cmake_indent_end_regex = '^\s*\(ENDIF\|ENDFOREACH\|ENDMACRO\|ELSE\|ENDWHILE\)\s*('
 
   " Add
   if previous_line =~? cmake_indent_comment_line " Handle comments