Change references of 'EMail' to '[Ee]mail'

Depending on if it was the beginning of the sentence the EMail would
become 'Email' or 'email'.

Some references of 'Email' were changed to 'email' as well as those were
not in the beginning of a sentence.

A few places some consistency of capitalised email address (made lower
case) were changed to match other places of the same pattern.

1992/mkentry.c

@@ -44,7 +44,7 @@
  * The rules and the guidelines may (and often do) change from year to
  * year.  You should be sure you have the current rules and guidelines
  * prior to submitting entries.  The IOCCC rules, guidelines and mkentry
- * program may be obtained from the judges using the Email address above.
+ * program may be obtained from the judges using the email address above.
  * Please use the following subject when sending in your request:
  *
  *	send rules
@@ -199,7 +199,7 @@ main(argc, argv)
     printf("Email your entries to:\n");
     printf("\t%s\n", ENTRY_ADDR1);
     printf("\t%s\n\n", ENTRY_ADDR2);
-    printf("Please use the following subject when you Email your entry:\n");
+    printf("Please use the following subject when you email your entry:\n");
     printf("\tioccc entry\n\n");
     /* all done */
     exit(0);
@@ -715,7 +715,7 @@ output_author(output, oname)
      */
     printf("\nEnter information about each author.  If your entry is after\n");
     printf("%s and before the contest deadline, the judges\n", START_DATE);
-    printf("will attempt to Email back a confirmation to the first author\n");
+    printf("will attempt to email back a confirmation to the first author\n");
 
     /*
      * place author information for each author in an individual section
@@ -751,9 +751,9 @@ output_author(output, oname)
 	printf("your country and do not include your name.\n");
 	output_till_dot(output, oname, "addr:");
 
-	/* write the Email address */
+	/* write the email address */
 	printf(
-	    "\nEnter the Email address for author #%d.  Use an address from\n",
+	    "\nEnter the email address for author #%d.  Use an address from\n",
 	    auth_cnt);
 	printf(
 	    "a registered domain or well known site.  If you give several\n");