patch 9.0.1990: strange error number

Problem:  strange error number
Solution: change error number,
          add doc tag for E1507

closes: #13270

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Christ van Willegen <cvwillegen@gmail.com>
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 6eecd7a..a4eb95e 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -6884,6 +6884,14 @@
 <			E1505: Invalid format specifier:
 			%1$d at width %2$d is: %01$*2$.3$d
 
+							*E1507*
+		This internal error indicates that the logic to
+		parse a positional format error ran into a problem
+		that couldn't be otherwise reported. Please file a
+		bug against vim if you run into this, copying the
+		exact format string and parameters that were used.
+
+
 prompt_getprompt({buf})					*prompt_getprompt()*
 		Returns the effective prompt text for buffer {buf}.  {buf} can
 		be a buffer name or number.  See |prompt-buffer|.
diff --git a/runtime/doc/tags b/runtime/doc/tags
index c32b679..ca4eaf9 100644
--- a/runtime/doc/tags
+++ b/runtime/doc/tags
@@ -4510,6 +4510,7 @@
 E1504	builtin.txt	/*E1504*
 E1505	builtin.txt	/*E1505*
 E1506	editing.txt	/*E1506*
+E1507	builtin.txt	/*E1507*
 E1508	editing.txt	/*E1508*
 E1509	editing.txt	/*E1509*
 E151	helphelp.txt	/*E151*