Restructure configuration scheme for bfd, binutils, ld.

Restructure configuration scheme for bfd, binutils, ld.

* include/sys/h-*.h:  Move to bfd/hosts/h-*.h.
* configure.in:  Revise to symlink sysdep.h to hosts/h-xxx.h.
Change some config names to match other dirs.
* *.c:  Include bfd.h before sysdep.h, so ansidecl and PROTO()
get defined first.
* Makefile.in:  Use -I. to get sysdep.h.
* trad-core.c:  Don't disable the whole file if SUN4_SYS.
* config/:  Rename some config files to match up h-*.h names.
Remove all the HOST_SYS definitions from the config files.
* hosts/h-amix.h, h-i386v.h:  Define POSIX_UTIME, not USG.
* hosts/h-hp9000.h:  Remove USG comment.
* hosts/h-rs6000.h:  Include <stdlib.h> for malloc.
* hosts/h-news.h, h-sparc-64.h:  New config files that had
previously been kludged in the <sysdep.h> file.