sim: Add PRU simulator port

sim: Add PRU simulator port

A simulator port for the TI PRU I/O processor.

v1: https://sourceware.org/ml/gdb-patches/2016-12/msg00143.html
v2: https://sourceware.org/ml/gdb-patches/2017-02/msg00397.html
v3: https://sourceware.org/ml/gdb-patches/2017-02/msg00516.html
v4: https://sourceware.org/ml/gdb-patches/2018-06/msg00484.html
v5: https://sourceware.org/ml/gdb-patches/2019-08/msg00584.html
v6: https://sourceware.org/ml/gdb-patches/2019-09/msg00036.html

gdb/ChangeLog:

	* NEWS: Mention new simulator port for PRU.

sim/ChangeLog:

	* MAINTAINERS: Add myself as PRU maintainer.
	* configure: Regenerated.
	* configure.tgt: Add PRU.

sim/common/ChangeLog:

	* gennltvals.sh: Add PRU libgloss target.
	* nltvals.def: Regenerate from the latest libgloss sources.

sim/pru/ChangeLog:

	* Makefile.in: New file.
	* aclocal.m4: Regenerated.
	* config.in: Regenerated.
	* configure: Regenerated.
	* configure.ac: New file.
	* interp.c: New file.
	* pru.h: New file.
	* pru.isa: New file.
	* sim-main.h: New file.