Fix segfault in cs_option() on s390x

[iii-i]

capstone-rs crashes on s390x (also knows as SystemZ in the LLVM world)
as follows:

Thread 2 received signal SIGSEGV, Segmentation fault.
0x000002aa00a6a604 in cs_option (ud=140702726002672, type=CS_OPT_SYNTAX, value=2) at capstone/cs.c:782
782             return arch_configs[handle->arch].arch_option(handle, type, value);

(gdb) p/x handle->arch
$7 = 0x7ffb

handle->arch is clearly corrupted. It is assigned as follows in
cs_open():

   0x000002aa00a6a44a <+146>:   lgr     %r9,%r3
[...]
   0x000002aa00a6a468 <+176>:   rosbg   %r9,%r10,0,31,32
[...]
458                     ud->arch = arch;
459                     ud->mode = mode;
   0x000002aa00a6a47a <+194>:   stg     %r9,0(%r13)

Here the 32-bit arch value and the 32-bit mode value are placed into a
64-bit register and stored with one instruction.

The important part is that cs_mode is a 32-bit value passed in %r3, and
the code uses instructions with mnemonics ending with "g", which
operate on full 64-bit registers [1]. This is allowed because of the
s390x ABI [1]: it requires zero-extension of 4-byte int arguments.

Bitfield enums are currently generated like this:

#[repr(C)]
[...]
pub struct cs_mode(pub libc::c_uint);

which causes the problem above, because the ABI does not require
zero-extension of 4-byte struct arguments.

Starting from RustTarget::Stable_1_28, bindgen
generates #[repr(transparent)] instead of #[repr(C)], which is
designed to solve exactly this kind of problems [3].

capstone-rs' MSRV is 1.70, so it should be possible to go even further,
but be conservative and use the minimum version necessary to fix the
issue.

[1] https://publibfp.dhe.ibm.com/epubs/pdf/a227832d.pdf
[2] https://github.com/IBM/s390x-abi/releases
[3] https://doc.rust-lang.org/nomicon/other-reprs.html#reprtransparent

[iii-i]

• Fixed a couple typos.

[iii-i]

• (Hopefully) fixed a clippy warning in unrelated code.

[iii-i]

• Local testing with nightly has produced even more clippy warnings; fixed all of them.

[tmfink]

Thanks for the PR! Your comments are very descriptive.
I'll try to review your changes, but no promises on the timeline.