Ignore spurious Delete key press during info screen

When a user reboots the system using Ctrl+Alt+RShift+Delete and keeps
the keys pressed for too long, we might see a spurious Delete key press.
Previously, this immediately exited the info screen.

Thank you to Exxos for reporting this.

Note that spurious Ctrl, Alt and Shift key presses are handled in
ikbd_reset(), but the Delete key press only arrives much later.

bios/initinfo.c

@@ -44,6 +44,9 @@
 
 #if FULL_INITINFO
 
+#define ESC_ASCII   0x1b
+#define DEL_ASCII   0x7f
+
 #define INFO_LENGTH 40      /* width of info lines (must fit in low-rez) */
 #define LOGO_LENGTH 34      /* must equal length of strings in EmuTOS logo */
 
@@ -374,6 +377,10 @@ WORD initinfo(ULONG *pshiftbits)
      * pause for a short while, or longer if:
      *  . a Shift key is held down, or
      *  . the user selects an alternate boot drive
+     *
+     * if the user reboots using Ctrl+Alt+Shift+Delete,
+     * and keeps the keys pressed for too long, we might see a
+     * spurious Del key press, and ignore it.
      */
     while (1)
     {
@@ -410,8 +417,12 @@ WORD initinfo(ULONG *pshiftbits)
             int c = LOBYTE(bconin2());
 
             c = toupper(c);
+            if (c == DEL_ASCII) {
+                /* eat spurious Delete key press */
+                continue;
+            } else
 #if WITH_CLI
-            if (c == 0x1b) {
+            if (c == ESC_ASCII) {
                 bootflags |= BOOTFLAG_EARLY_CLI;
             } else
 #endif