[GDBSYM] Remove unused gdbsym.c

The GDBSYM config.h option was an attempt at QEMU GDB debugging.  I have
removed the code since it is unused and may confuse people wanting to
use the GDB stub.

src/arch/i386/core/gdbsym.c

-#include <stdio.h>
-#include <gpxe/init.h>
-#include <console.h>
-#include <realmode.h>
-
-extern char __text[];
-extern char __rodata[];
-extern char __data[];
-extern char __bss[];
-extern char __text16[];
-extern char __data16[];
-
-
-static void gdb_symbol_line ( void ) {
-	printf ( "Commands to start up gdb:\n\n" );
-	printf ( "gdb\n" );
-	printf ( "target remote localhost:1234\n" );
-	printf ( "set confirm off\n" );
-	printf ( "add-symbol-file symbols %#lx", virt_to_phys ( __text ) );
-	printf ( " -s .rodata %#lx", virt_to_phys ( __rodata ) );
-	printf ( " -s .data %#lx", virt_to_phys ( __data ) );
-	printf ( " -s .bss %#lx", virt_to_phys ( __bss ) );
-	printf ( " -s .text16 %#x", ( ( rm_cs << 4 ) + (int)__text16 ) );
-	printf ( " -s .data16 %#x", ( ( rm_ds << 4 ) + (int)__data16 ) );
-	printf ( "\n" );
-	printf ( "add-symbol-file symbols 0\n" );
-	printf ( "set confirm on\n" );
-	getkey();
-}
-
-struct startup_fn gdb_startup_fn __startup_fn ( STARTUP_NORMAL ) = {
-	.startup = gdb_symbol_line,
-};

src/config.h

 #undef	BUILD_ID		/* Include a custom build ID string,
 				 * e.g "test-foo" */
 #undef	NULL_TRAP		/* Attempt to catch NULL function calls */
-#undef	DUMP_GDBSYM		/* Dump GDB symbol table information */
 
 /* @END general.h */

src/core/config.c

 #ifdef NULL_TRAP
 REQUIRE_OBJECT ( nulltrap );
 #endif
-#ifdef DUMP_GDBSYM
-REQUIRE_OBJECT ( gdbsym );
-#endif