patch 8.2.1933: cannot sort using locale ordering

Problem:    Cannot sort using locale ordering.
Solution:   Add a flag for :sort and sort() to use the locale. (Dominique
            Pellé, closes #7237)
diff --git a/runtime/doc/change.txt b/runtime/doc/change.txt
index fe62d1d..12e20a5 100644
--- a/runtime/doc/change.txt
+++ b/runtime/doc/change.txt
@@ -1801,7 +1801,7 @@
 found here: |sort()|, |uniq()|.
 
 							*:sor* *:sort*
-:[range]sor[t][!] [b][f][i][n][o][r][u][x] [/{pattern}/]
+:[range]sor[t][!] [b][f][i][l][n][o][r][u][x] [/{pattern}/]
 			Sort lines in [range].  When no range is given all
 			lines are sorted.
 
@@ -1809,6 +1809,14 @@
 
 			With [i] case is ignored.
 
+			With [l] sort uses the current locale. See
+			`language collate` to check or set the locale used
+			for ordering. For example, with "en_US.UTF8",
+			Ö will be ordered after O and before P,
+			whereas with the Swedish locale "sv_SE.UTF8",
+			it will be after Z.
+			Case is typically ignored by the locale.
+
 			Options [n][f][x][o][b] are mutually exclusive.
 
 			With [n] sorting is done on the first decimal number
@@ -1875,8 +1883,7 @@
 Note that using `:sort` with `:global` doesn't sort the matching lines, it's
 quite useless.
 
-The details about sorting depend on the library function used.  There is no
-guarantee that sorting obeys the current locale.  You will have to try it out.
+`:sort` does not use the current locale unless the l flag is used.
 Vim does do a "stable" sort.
 
 The sorting can be interrupted, but if you interrupt it too late in the
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index b757e5f..e487d3e 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -9700,6 +9700,13 @@
 		When {func} is given and it is '1' or 'i' then case is
 		ignored.
 
+		When {func} is given and it is 'l' then the current locale
+		is used for ordering. See `language collate` to check or set
+		the locale used for ordering.  For example, with "en_US.UTF8",
+		Ö will be ordered after O and before P, whereas with the
+		Swedish locale "sv_SE.UTF8", it will be after Z.
+		Case is typically ignored by the locale.
+
 		When {func} is given and it is 'n' then all items will be
 		sorted numerical (Implementation detail: This uses the
 		strtod() function to parse numbers, Strings, Lists, Dicts and