gdb: make jit.c use the inferior_created inferior parameter

gdb: make jit.c use the inferior_created inferior parameter

Use the inferior parameter now available in jit_inferior_created_hook.
It is passed down to jit_inferior_init, which uses it as much as
possible instead of the current inferior or current program space.

gdb/ChangeLog:

	* jit.c (jit_reader_load_command): Pass current inferior.
	(jit_inferior_init): Change parameter type to inferior, use it.
	(jit_inferior_created): Remove.
	(jit_inferior_created_hook): Pass inferior parameter down.
	(_initialize_jit): Use jit_inferior_created_hook instead of
	jit_inferior_created.
	* jit.h (jit_inferior_created_hook): Add inferior parameter.
	* infrun.c (follow_exec): Pass inferior to
	jit_inferior_created_hook.

Change-Id: If3a2114a933370dd313d5abd623136d273cdb8fa