x86.{c,h}: opcode-based x86 instruction analysis (NOT a disassembler)

Currently only handles opcodes found in basic 32-bit userspace functions;
there’s no kernel-mode instructions, no SSE 3+, no AVX, no REX (64-bit), no
EVEX, yadda yadda.

Subject to extension later if there’s ever a use for it.

== Compiling ==

  gcc -c -O2 [-flto] x86.c
  clang -c -O2 [-flto] x86.c
  tcc -c x86.c
  cl.exe /c /O2 x86.c

In most cases you can just drop the .c file straight into your codebase/build
system. LTO is advised to avoid dead code and enable more efficient calls
including potential inlining.

== Compiler compatibility ==

- Any reasonable GCC
- Any reasonable Clang
- Any reasonable MSVC
- TinyCC
- Probably almost all others; this is very portable code

Note that GCC and Clang will generally give the best-performing output.

Once the .c file is built, the public header can be consumed by virtually any C
or C++ compiler, as well as probably most half-decent FFIs.

Note that the .c source file is probably C++-compatible at the moment, but this
is not guaranteed, so it's best to compile it as a C source. The header will
work fine from either language.

== API usage ==

See documentation comments in x86.h for a basic idea. Some *pro tips*:

== OS compatibility ==

- All.
- Seriously, this library doesn’t even use libc.

== Architecture compatibility ==

- All, so long as char is 8 bits.

== Copyright ==

The source file and header both fall under the ISC licence — read the notices in
both of the files for specifics.

Thanks, and have fun!
- Michael Smith <mikesmiffy128@gmail.com>