[PATCH v2 0/9] RISC-V: Support version controling for ISA standard extensions and CSR

[Nelson Chu <nelson.chu@sifive.com>]

Hi binutils and gdb,

After getting some good feedbacks, I refactor the series of patches.
These patches are tested and get toolchain regressions pass.
There are some differences from the last version,

1. Remove the -mriscv-isa-version and --with-riscv-isa-version options.
We can still use -march to choose the version for each extensions, so there is
no need to add these.

2. Change the arguments of options from [1p9|1p9p1|...] to [1.9|1.9.1|...].
Unlike the architecture string has specified by spec, ther is no need to do
the same thing for options.

3. Spilt the patches to reduce the burdens of review.

[PATCH 3/7] RISC-V: Support new GAS options and configure options to set ISA versions
to
[PATCH v2 3/9] RISC-V: Support GAS option -misa-spec to set ISA versions
[PATCH v2 4/9] RISC-V: Support configure options to set ISA versions by default.

[PATCH 4/7] RISC-V: Support version checking for CSR according to privilege version.
to
[PATCH v2 5/9] RISC-V: Support version checking for CSR according to privilege spec version.
[PATCH v2 6/9] RISC-V: Support configure option to choose the privilege spec version.

4. Use enum class rather than string to compare the choosen ISA spec in opcodes/riscv-opc.c.
The behavior is same as comparing the choosen privilege spec.

Thanks
Nelson