This commit is the first commit among a series of patches that implement the
compile-time architecture tag proposal in capstone-rust#118. It contains the following major
changes:

- Add the ArchTag trait. This trait indicates a "tag" type that represents a
  specific architecture. Its associated types specify specific data types
  corresponding to the architecture it represents.

- Add ArchTag implementations for supported architectures, and a special
  DynamicArchTag that indicates the target architecture is unknown at compile
  time.

- Update existing general type definitions (e.g. Capstone, Insn, etc.) to
  acquire a general arch tag type parameter.

This commit changes the bindgen settings so that bindgen generates newtype enums
instead of modules of constants for arch insn group types and reg types. Usages
of these binding types are updated as well.

…chTag>

This commit contains changes that make existing examples and benches compile
with the latest API design. Unit tests will be covered in later commits.

The primary changes include:
- Implement DetailArchInsn for ArchDetail.
- Add ArchOperandIterator enum that iterates values of ArchOperand inside an
  ArchDetail. The enum is basically a wrapper that holds all available arch-
  specific operand iterators in different variants.

This commit also contains some refactors and minor changes, including:
- Rename ArchDetail to ArchInsnDetail as the old name is a bit confusing.
- Fully add sysz support.
- Update existing examples and benches. In most cases, to migrate these existing
  examples and benches, I just need to add a small number of generic type
  arguments (e.g. X86ArchTag, ArmArchTag, DynamicArchTag, etc.) and the code
  just compiles.

This commit fixes a minor problem that prevents tests from compiling and running
to success.

Arch-specific register IDs (represented by ArchTag::RegId) and instruction group
IDs (represented by ArchTag::InsnGroupId) are generated as newtype structs whose
inner type is c_uint because their C definition are just C enums. However, in a
cs_detail struct, the regs_read field is an array of u16, not an array of
c_uint. So we cannot just type pun on the underlying array to get &[A::RegId]
because the layout is totally different. The similar problem exists for
InsnDetail::regs_write and InsnDetail::groups.

This commit fixes the problem by making these function return an Iterator rather
than a slice. The iterator will map the underlying array elements to actual
arch-specific types when iterated.