patch 8.1.0528: various typos in comments

Problem:    Various typos in comments.
Solution:   Fix the typos.
diff --git a/src/gui_mac.c b/src/gui_mac.c
index aa093a3..96f04c5 100644
--- a/src/gui_mac.c
+++ b/src/gui_mac.c
@@ -2278,7 +2278,7 @@
     if (p_mh)
 	ObscureCursor();
 
-    /* Get the key code and it's ASCII representation */
+    /* Get the key code and its ASCII representation */
     key_sym = ((theEvent->message & keyCodeMask) >> 8);
     key_char = theEvent->message & charCodeMask;
     num = 1;
@@ -2597,7 +2597,7 @@
 bail:
     /*
      * when we fail give any additional callback handler a chance to perform
-     * it's actions
+     * its actions
      */
     return CallNextEventHandler(nextHandler, theEvent);
 }