patch 8.1.0231: :help -? goes to help for -+

Problem:    :help -? goes to help for -+.
Solution:   Add -? to list of special cases. (Hirohito Higashi)

src/ex_cmds.c

@@ -6583,7 +6583,7 @@ find_help_tags(
     static char *(mtable[]) = {"*", "g*", "[*", "]*", ":*",
 			       "/*", "/\\*", "\"*", "**",
 			       "cpo-*", "/\\(\\)", "/\\%(\\)",
-			       "?", ":?", "?<CR>", "g?", "g?g?", "g??",
+			       "?", ":?", "-?", "?<CR>", "g?", "g?g?", "g??",
 			       "/\\?", "/\\z(\\)", "\\=", ":s\\=",
 			       "[count]", "[quotex]",
 			       "[range]", ":[range]",
@@ -6593,7 +6593,7 @@ find_help_tags(
     static char *(rtable[]) = {"star", "gstar", "[star", "]star", ":star",
 			       "/star", "/\\\\star", "quotestar", "starstar",
 			       "cpo-star", "/\\\\(\\\\)", "/\\\\%(\\\\)",
-			       "?", ":?", "?<CR>", "g?", "g?g?", "g??",
+			       "?", ":?", "-?", "?<CR>", "g?", "g?g?", "g??",
 			       "/\\\\?", "/\\\\z(\\\\)", "\\\\=", ":s\\\\=",
 			       "\\[count]", "\\[quotex]",
 			       "\\[range]", ":\\[range]",

src/testdir/test_help_tagjump.vim

@@ -26,6 +26,11 @@ func Test_help_tagjump()
   call assert_true(getline('.') =~ '\*:?\*')
   helpclose
 
+  help -?
+  call assert_equal("help", &filetype)
+  call assert_true(getline('.') =~ '\*-?\*')
+  helpclose
+
   help FileW*Post
   call assert_equal("help", &filetype)
   call assert_true(getline('.') =~ '\*FileWritePost\*')

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    231,
 /**/
     230,
 /**/