libcyaml: update to 1.3.1.

## LibCYAML v1.3.1

* **Loading**:
  * Fixed value out-of-range detection limits for signed integers.

## LibCYAML v1.3.0

* **Saving**:
  * New flags allow control over scalar output style.
    - For example to force single or double quote style.
* **General**:
  * Buildsystem changes to allow use of CPPFLAGS from the environment.

## LibCYAML v1.2.1

* **General**:
  * Support for dynamic library build on Mac OS X.
  * Ordered designated initialisers in public header for C++ compatibility.

(wiz)