[build] Use PRODUCT_SHORT_NAME for end-user visible strings

Use PRODUCT_SHORT_NAME instead of a hardcoded "iPXE" for strings which
are typically shown in the user interface.

Note that this only allows for customisation of the user interface.
Where the "iPXE" string serves a technical purpose (such as in the
HTTP User-Agent), the string cannot be customised.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/prefix/romprefix.S

 	.ascii	"\n"
 	.ascii	PRODUCT_NAME
 	.ascii	"\n"
-	.asciz	"iPXE (http://ipxe.org)"
+	.ascii	PRODUCT_SHORT_NAME
+	.asciz	" (http://ipxe.org)"
 	.size	init_message, . - init_message
 .ifeqs	BUSTYPE, "PCIR"
 init_message_pci:

src/hci/shell.c

 #include <ipxe/command.h>
 #include <ipxe/parseopt.h>
 #include <ipxe/shell.h>
+#include <config/branding.h>
 
 /** @file
  *
  */
 
 /** The shell prompt string */
-static const char shell_prompt[] = "iPXE> ";
+static const char shell_prompt[] = PRODUCT_SHORT_NAME "> ";
 
 /**
  * "help" command

src/hci/tui/settings_ui.c

 #include <ipxe/keys.h>
 #include <ipxe/ansicol.h>
 #include <ipxe/settings_ui.h>
+#include <config/branding.h>
 
 /** @file
  *
 	clearmsg ( TITLE_ROW );
 	name = settings_name ( widget->settings );
 	attron ( A_BOLD );
-	msg ( TITLE_ROW, "iPXE configuration settings%s%s",
+	msg ( TITLE_ROW, PRODUCT_SHORT_NAME " configuration settings%s%s",
 	      ( name[0] ? " - " : "" ), name );
 	attroff ( A_BOLD );
 }

src/usr/autoboot.c

 #include <usr/prompt.h>
 #include <usr/autoboot.h>
 #include <config/general.h>
+#include <config/branding.h>
 
 /** @file
  *
 
 	/* Prompt user */
 	printf ( "\n" );
-	return ( prompt ( "Press Ctrl-B for the iPXE command line...",
+	return ( prompt ( "Press Ctrl-B for the " PRODUCT_SHORT_NAME
+			  " command line...",
 			  ( ( BANNER_TIMEOUT * TICKS_PER_SEC ) / 10 ),
 			  CTRL_B ) == 0 );
 }
 	 * do so.
 	 *
 	 */
-	printf ( NORMAL "\n\n%s\n" BOLD "iPXE %s"
+	printf ( NORMAL "\n\n" PRODUCT_NAME "\n" BOLD PRODUCT_SHORT_NAME " %s"
 		 NORMAL " -- Open Source Network Boot Firmware -- "
 		 CYAN "http://ipxe.org" NORMAL "\n"
-		 "Features:", product_name, product_version );
+		 "Features:", product_version );
 	for_each_table_entry ( feature, FEATURES )
 		printf ( " %s", feature->name );
 	printf ( "\n" );