patch 9.0.1212: cannot read back what setcellwidths() has done

Problem:    Cannot read back what setcellwidths() has done.
Solution:   Add getcellwidths(). (Kota Kato, closes #11837)
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index f202da0..3544b5d 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -211,6 +211,7 @@
 getbufoneline({buf}, {lnum})	String	line {lnum} of buffer {buf}
 getbufvar({buf}, {varname} [, {def}])
 				any	variable {varname} in buffer {buf}
+getcellwidths()			List	get character cell width overrides
 getchangelist([{buf}])		List	list of change list items
 getchar([expr])			Number or String
 					get one character from the user
@@ -3262,6 +3263,13 @@
 <		Can also be used as a |method|: >
 			GetBufnr()->getbufvar(varname)
 <
+getcellwidths()						*getcellwidths()*
+		Returns a |List| of cell widths of character ranges overridden
+		by |setcellwidths()|.  The format is equal to the argument of
+		|setcellwidths()|.  If no character ranges have their cell
+		widths overridden, an empty List is returned.
+
+
 getchangelist([{buf}])					*getchangelist()*
 		Returns the |changelist| for the buffer {buf}. For the use
 		of {buf}, see |bufname()| above. If buffer {buf} doesn't
@@ -9969,7 +9977,7 @@
 		Return a string representation of the type of {expr}.
 		Example: >
 			echo typename([1, 2, 3])
-			list<number>
+<			list<number> ~
 
 
 undofile({name})					*undofile()*