debug compile: Replace confusing debug message

debug compile: Replace confusing debug message

It was found that from

(gdb) set debug compile 1
(gdb) compile code 1
[...]
allocated 0x7f bytes at 0x7ffff7ff9000 prot 5
allocated 0x38 bytes at 0x7ffff7ff8000 prot 1
lookup undefined ELF symbol "_GLOBAL_OFFSET_TABLE_"
allocated 0x10 bytes at 0x7ffff7ff7000 for registers
(gdb) _

the message 'lookup undefined ELF symbol' looks as an error to people,
including to myself once.

Change it to:

allocated 0x7f bytes at 0x7ffff7ff9000 prot 5
allocated 0x38 bytes at 0x7ffff7ff8000 prot 1
ELF symbol "_GLOBAL_OFFSET_TABLE_" relocated to zero
allocated 0x10 bytes at 0x7ffff7ff7000 for registers
(gdb) _

gdb/ChangeLog
2015-07-02  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* compile/compile-object-load.c (compile_object_load): Replace debug
	message "lookup undefined ELF symbol" by 3 more specific messages.