* configure.in (i?86-*-beos{pe,elf,}*): Recognize.
* i386/t-beos, i386/x-beos, i386/xm-beos.h: New files.
* i386/beos-elf.h, i386/beos-pe.h: New files.
* Makefile.in (CROSS_SYSTEM_HEADER_DIR): New.
* cross-make (SYSTEM_HEADER_DIR): Define using
CROSS_SYSTEM_HEADER_DIR.
* gcc.c (LIBRARY_PATH_ENV): Provide default.
(process_command): Use it.
(main): Likewise. Kill trailing = from env vars.
(build_search_list): Put it back.
* collect2.c (main): Use LIBRARY_PATH_ENV.
* configure.in (GCC_NEED_DECLARATIONS): Add environ.
* toplev.c: Use NEED_DECLARATION_ENVIRON.