Pass pointers to nativeint values as intnat*, not int*, in the tests.
Remove struct subtyping example.
Install C header files.
Merge pull request #122 from yallop/install-headers

Install C header files.
Use absolute path for compiling C source files.
Print bigarray types using the C type syntax.
Remove duplicate typedefs.
Expose a type equality for Ctypes.ptr.
Add a function ctypes_copy_bytes for building GC-managed blocks.
Compute external names for types in Ctypes_bigarray.
Give views and structured types an identity.
Add ctypes.stubs subpackage.
Add a module for validating and printing paths.
Add the cstubs project to the Makefile.
Definitions of errors raised during stub generation.
C stub generation.
Add a single header file with everything needed by generated stubs.
A module for registering paths for views and structured types.
A module with the types and functions used by generated stubs.
Generate 'external' declarations and ML wrapper functions.