Use "<enter>" instead of "return" or "enter" in input prompts

This should make it more clear we are talking about the key and not
something else.

debian/changelog

@@ -86,6 +86,7 @@ dpkg (1.18.0) UNRELEASED; urgency=low
     - Say “package” instead of “it” in dpkg-name warning message.
     - Uppercase field names in error messages.
     - Expand EOF and eof into “end of file” in error messages.
+    - Use “<enter>” instead of “return” or “enter” in input prompts.
 
   [ Raphaël Hertzog ]
   * Drop myself from Uploaders.

dselect/methods/ftp/setup.pl

@@ -171,7 +171,7 @@ store_config("$methdir/vars");
 chmod  0600, "$methdir/vars";
 
 if($exit || $problem) {
-    print "Press return to continue\n";
+    print "Press <enter> to continue\n";
     <STDIN>;
 }
 

scripts/dpkg-buildpackage.pl

@@ -601,7 +601,7 @@ if ($check_command) {
 }
 
 if ($signpause && ($signchanges || $signsource)) {
-    print g_("Press the return key to start signing process\n");
+    print g_("Press <enter> to start the signing process.\n");
     getc();
 }
 

utils/update-alternatives.c

@@ -1614,7 +1614,7 @@ alternative_select_choice(struct alternative *a)
 		for (fs = a->choices; fs; fs = fs->next, idx++)
 			alternative_print_choice(a, ALT_ST_MANUAL, fs, idx, len);
 		printf("\n");
-		printf(_("Press enter to keep the current choice[*], "
+		printf(_("Press <enter> to keep the current choice[*], "
 		         "or type selection number: "));
 		ret = fgets(selection, sizeof(selection), stdin);
 		if (ret == NULL || strlen(selection) == 0) {