[elf] Add execution entry point debug messages for elf/multiboot images

src/arch/i386/image/elfboot.c

 	shutdown ( SHUTDOWN_BOOT );
 
 	/* Jump to OS with flat physical addressing */
+	DBGC ( image, "ELF %p starting execution at %lx\n", image, entry );
 	__asm__ __volatile__ ( PHYS_CODE ( "call *%%edi\n\t" )
 			       : : "D" ( entry )
 			       : "eax", "ebx", "ecx", "edx", "esi", "ebp",

src/arch/i386/image/multiboot.c

 	shutdown ( SHUTDOWN_BOOT );
 
 	/* Jump to OS with flat physical addressing */
+	DBGC ( image, "MULTIBOOT %p starting execution at %lx\n",
+	       image, entry );
 	__asm__ __volatile__ ( PHYS_CODE ( "call *%%edi\n\t" )
 			       : : "a" ( MULTIBOOT_BOOTLOADER_MAGIC ),
 			           "b" ( virt_to_phys ( &mbinfo ) ),