patch 8.2.3071: shell options are not set properly for PowerShell

Problem:    Shell options are not set properly for PowerShell.
Solution:   Use better option defaults. (Mike Willams, closes #8459)
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 4356381..7fb2534 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -9878,9 +9878,11 @@
 
 shellescape({string} [, {special}])			*shellescape()*
 		Escape {string} for use as a shell command argument.
-		On MS-Windows, when 'shellslash' is not set, it will enclose
-		{string} in double quotes and double all double quotes within
-		{string}.
+		On MS-Windows, when the 'shell' contains powershell then it
+		will enclose {string} in single quotes and will double up all
+		internal single quotes.  With other values for 'shell' when
+		'shellslash' is not set, it will enclose {string} in double
+		quotes and double all double quotes within {string}.
 		Otherwise it will enclose {string} in single quotes and
 		replace all "'" with "'\''".
 
@@ -11040,7 +11042,8 @@
 			:exe "redir > " . tmpfile
 <		For Unix, the file will be in a private directory |tempfile|.
 		For MS-Windows forward slashes are used when the 'shellslash'
-		option is set or when 'shellcmdflag' starts with '-'.
+		option is set or when 'shellcmdflag' starts with '-' except
+		when when 'shell' contains powershell.
 
 
 term_ functions are documented here: |terminal-function-details|