* i386-linux-nat.c (ORIG_EAX): Define to -1 if not already

* i386-linux-nat.c (ORIG_EAX): Define to -1 if not already
defined.
(regmap): Extend to cover all registers.
(PT_READ_U, PT_WRITE_U, PTRACE_XFER_TYPE,
OLD_CANNOT_FETCH_REGISTERS, OLD_CANNOT_STORE_REGISTERS): Remove
definitions.
(fetch_register, sore_register): Simplify.
(old_fetch_inferior_registers, old_store_inferior_registers):
Remove functions.
(cannot_fetch_register, cannot_store_register): Change
implementation to use regmap array to decide which registers
cannot be fetched/stored.  This removes $orig_eax from the
registers that cannot be fetched/stored.
(fetch_inferior_registers): Call fetch_register directly instead
of calling old_fetch_inferior_registers.
(store_inferior_registers): Call store_register directly instead
of calling old_store_inferior_registers.
(i386_linux_dr_get): Replace PT_READ_U with PTRACE_PEEKUSER.
(i386_linux_dr_set): Replace PT_WRITE_U with PTRACE_POKEUSER.
* config/i386/nm-linux.h (U_REGS_OFFSET): Remove definition.