patch 8.2.1435: Vim9: always converting to string for ".." leads to mistakes

Problem:    Vim9: always converting to string for ".." leads to mistakes.
Solution:   Only automatically convert simple types.
diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index 7c4a64f..f9fd136 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -426,11 +426,14 @@
 	2 && 0   == 0
 	[] && 2  == []
 
-When using `..` for string concatenation the arguments are always converted to
-string. >
+When using `..` for string concatenation arguments of simple types are always
+converted to string. >
 	'hello ' .. 123  == 'hello 123'
 	'hello ' .. v:true  == 'hello true'
 
+Simple types are string, float, special and bool.  For other types |string()|
+can be used.
+
 In Vim9 script one can use "true" for v:true and "false" for v:false.
 
 
@@ -805,6 +808,9 @@
 	   ...
 <   This goes in .../import/someother.vim.
 
+When compiling a `:def` function and a function in an autoload script is
+encountered, the script is not loaded until the `:def` function is called.
+
 
 Import in legacy Vim script ~