* Builds were failing because of a "no rule to make target buildopt.lo,
  needed by libmpfr.la".
* It seems that this problem may be due to cached files...

* Commit GMP 5.1.1, MPC 1.0.1, and MPFR 3.1.2 as required to build GCC.
  (config.sub and configfsf.sub are variously modified to support
   RISC-V.)
* Modify Makefile.in for native building support.
* Add instructions to README.
* Add gcc hackish patch to define SSIZE_MAX.
* Direct the bitsperlong.h Linux header to consult _RISCV_SIM rather
  than __riscv{64,32}, because __riscv32 doesn't exist.
* Initialize status to 0 in binutils/opcodes/riscv-dis.c to silence a
  GCC warning.

* Parallel headers in riscv-linux commit a5fe6bf149.
* Remove .install and ..install.cmd files.

When disassembling invalid code, it's possible to read off the end of a
section.  As long as the address is valid, don't treat that as an error.

This reverts commit 35fe8c1b.

ra then s0 will always be at the top of the frame for ease of backtracing.

* Seems to correctly place ld.so.1's relocations into .data.rel.ro
  and not .rodata.
* .rodata is no longer marked with the W flag in readelf -S output
  for ld.so.1.
* I don't fully understand this commit.

* Prevents (or at least so I think) register %4 from being reused.
* Fixes problem in which busybox attempts this snippet of code:
  1:   lr.w    v1, 0(a1)
        bne    v1, a2, 1f
       sc.w    a1, v0, 0(a1)
       bnez    a1, 1b
  1:
  If sc.w fails, a1 receives 1, and the lr.w is attempted again.

* Update linux-headers for changed register usage.
* Fixes "can't fork" problems in Busybox.

This also fixes the erroneous emission of a call instead of a sibcall.

use JAL instead of AUIPC/LD/JALR