client-lib: Remove wrong static declaration of C RPC client.
bindings-pkcs11: Update other files to reflect byte->char renaming of functions.

      - pkcs11.h
      - pkcs11.ml
      - pkcs11.mli
      - pkcs11_stubs.c
client-lib: Restore packing in the WIN32 case.
client-lib: Update IDL files related to previous patch:

  - related to Exclude OCaml headers when compiling C RPC.
client-lib: Initial WIN32 support.