vim-patch:8.0.1792: MS-Windows users expect -? to work like --help

Problem:    MS-Windows users expect -? to work like --help.
Solution:   Add -?. (Christian Brabandt, closes vim/vim#2867)
c3e81694fc

Include runtime/ changes from 85eee130f4 to pass 8.1.0231 tests.

runtime/doc/starting.txt

@@ -76,7 +76,8 @@ The option arguments may be given in any order.  Single-letter options can be
 combined after one dash.  There can be no option arguments after the "--"
 argument.
 
---help							*-h* *--help*
+--help							*-h* *--help* *-?*
+-?
 -h		Give usage (help) message and exit.
 		See |info-message| about capturing the text.
 

src/nvim/main.c

@@ -892,6 +892,7 @@ static void command_line_scan(mparm_T *parmp)
           set_option_value("rl", 1L, NULL, 0);
           break;
         }
+        case '?':    // "-?" give help message (for MS-Windows)
         case 'h': {  // "-h" give help message
           usage();
           mch_exit(0);