- various updates for GCC 7 riscv definitions: -mabi and -march changed
- add missing LIBGCC_MACHINE_ARCH
- add the new ldscripts for riscv64 MKCOMPAT.

Support building the xorg X11 libraries under MKCOMPAT.
Add XORG_MACHINE_ARCH to compat's bsd.*.mk
Turn xorg makekeys and makestrs into real host tools which are installed into
${TOOLSDIR}

New files for Userland support of UCB RISC-V (both 32-bit and 64-bit)