Rename gdbserver's low-level Linux x86 debug register accessors

Rename gdbserver's low-level Linux x86 debug register accessors

This commit renames gdbserver's low-level Linux x86 debug register
accessors to the same names used by GDB.

gdb/gdbserver/ChangeLog:

	* linux-x86-low.c (x86_dr_low_set_addr): Rename to...
	(x86_linux_dr_set_addr): ...this.
	(x86_dr_low_get_addr): Rename to...
	(x86_linux_dr_get_addr): ...this.
	(x86_dr_low_set_control): Rename to...
	(x86_linux_dr_set_control): ...this.
	(x86_dr_low_get_control): Rename to...
	(x86_linux_dr_get_control): ...this.
	(x86_dr_low_get_status): Rename to...
	(x86_linux_dr_get_status): ...this.
	(x86_dr_low): Update with new function names.