patch 8.2.0765: In the GUI can't use all the modifiers.

Problem:    In the GUI can't use all the modifiers. (Andri Möll)
Solution:   Do not apply Alt/Meta early, do it later like with the terminal.
            Avoid the Motif test from crashing.
diff --git a/src/gui_w32.c b/src/gui_w32.c
index 2409ee6..6527b42 100644
--- a/src/gui_w32.c
+++ b/src/gui_w32.c
@@ -847,8 +847,8 @@
     if (ch < 0x100 && !isalpha(ch) && isprint(ch))
 	modifiers &= ~MOD_MASK_SHIFT;
 
-    // Interpret the ALT key as making the key META, include SHIFT, etc.
-    ch = extract_modifiers(ch, &modifiers, TRUE, NULL);
+    // Unify modifiers somewhat.  No longer use ALT to set the 8th bit.
+    ch = extract_modifiers(ch, &modifiers, FALSE, NULL);
     if (ch == CSI)
 	ch = K_CSI;