Normalize names of the NetBSD files

Normalize names of the NetBSD files

The files used to be named 'nbsd', which incorrectly reflects
the name of the OS and confuses it with other BSD derived OSes.

gdb/ChangeLog:

        * Makefile.in (ALL_64_TARGET_OBS, ALL_TARGET_OBS)
        HFILES_NO_SRCDIR, ALLDEPFILES): Rename files.
        * alpha-bsd-nat.c: Adjust include.
        * alpha-bsd-tdep.h: Adjust comment.
        * alpha-nbsd-tdep.c: Rename to ...
        * alpha-netbsd-tdep.c: ... this, adjust include.
        * amd64-nbsd-nat.c: Rename to ...
        * amd64-netbsd-nat.c: ... this, adjust include.
        * amd64-nbsd-tdep.c: Rename to ...
        * amd64-netbsd-tdep.c: ... this, adjust include.
        * amd64-tdep.h: Adjust include.
        * arm-nbsd-nat.c: Rename to ...
        * arm-netbsd-nat.c: ... this, adjust include.
        * arm-nbsd-tdep.c: Rename to ...
        * arm-netbsd-tdep.c: ... this, adjust include.
        * arm-nbsd-tdep.h: Rename to ...
        * arm-netbsd-tdep.h: ... this, adjust include.
        * configure.nat: Adjust file lists.
        * configure.tgt: Likewise.
        * hppa-nbsd-nat.c: Rename to ...
        * hppa-netbsd-nat.c: ... this, adjust include.
        * hppa-nbsd-tdep.c: Rename to ...
        * hppa-netbsd-tdep.c: ... this, adjust include.
        * i386-nbsd-nat.c: Rename to ...
        * i386-netbsd-nat.c: ... this, adjust include.
        * i386-nbsd-tdep.c: Rename to ...
        * i386-netbsd-tdep.c: ... this, adjust include.
        * m68k-bsd-nat.c: Adjust include.
        * mips-nbsd-nat.c: Rename to ...
        * mips-netbsd-nat.c: ... this, adjust include.
        * mips-nbsd-tdep.c: Rename to ...
        * mips-netbsd-tdep.c: ... this, adjust include.
        * mips-nbsd-tdep.h: Rename to ...
        * mips-netbsd-tdep.h: ... this.
        * nbsd-nat.c: Rename to ...
        * netbsd-nat.c: ... this, adjust include.
        * nbsd-nat.h: Rename to ...
        * netbsd-nat.h: ... this, adjust include.
        * nbsd-tdep.c: Rename to ...
        * netbsd-tdep.c: ... this, adjust include.
        * nbsd-tdep.h: Rename to ...
        * netbsd-tdep.h: ... this.
        * ppc-nbsd-nat.c: Rename to ...
        * ppc-netbsd-nat.c: ... this, adjust include.
        * ppc-nbsd-tdep.c: Rename to ...
        * ppc-netbsd-tdep.c: ... this, adjust include and comment.
        * ppc-nbsd-tdep.h: Rename to ...
        * ppc-netbsd-tdep.h: ... this.
        * sh-nbsd-nat.c: Rename to ...
        * sh-netbsd-nat.c: ... this, adjust include.
        * sh-nbsd-tdep.c: Rename to ...
        * sh-netbsd-tdep.c: ... this, adjust include.
        * sparc-nbsd-nat.c: Rename to ...
        * sparc-netbsd-nat.c: ... this.
        * sparc-nbsd-tdep.c: Rename to ...
        * sparc-netbsd-tdep.c: ... this, adjust include.
        * sparc64-nbsd-nat.c: Rename to ...
        * sparc64-netbsd-nat.c: ... this.
        * sparc64-nbsd-tdep.c: Rename to ...
        * sparc64-netbsd-tdep.c: ... this, adjust include.
        * sparc64-tdep.h: Adjust comment.
        * vax-bsd-nat.c: Adjust include.
        * vax-nbsd-tdep.c: Rename to ...
        * vax-netbsd-tdep.c: ... this, adjust include.