SHVC version 0.4.0

Added
* `cptstodt` and `cpdttots` functions to `cp.h` to work with `struct
  timespec`.
* `cpdecexp` function and `cpitod` macro to `cp.h` for `struct
  cpdecimal`.
* `-s` argument to the `shvc` application to allow user ID to be
  initialized

Changed
* `fetch` method in RPCHistory now gives the application starting index
  and the number of records to be fetched, allowing better optimization
  from the application.
* Parameter and result type hints of the builtin method descriptions now
  follow RPC type hints defined in SHV standard.
* RPC client now uses standard `FILE` buffer for writing message with
  serial protocol and thus improving the performace.
* CPON and ChainPack packing and unpacking now uses unlocked read/write
  functions variants. This improves performace.

Removed
* No longer valid RPC error codes (they were removed from standard).
* `cpdecimal` and `cpdeccmp` as having invalid or no implementation.

Fixed
* RPC File's methods `sha1` and `crc` now correctly accept no parameter
  and single item in the list.
* Method `get` on `.device/alerts` path now correctly handles integer
  parameter.
* Double memory free error in rpccall.