Prepare 3.2.0

Merge pull request php-memcached-dev#507 from cmb69/cmb/libname

Adhere to standard naming convention of Windows libs for PHP

Prepare 3.2.0RC1

Bump version and release notes for 3.1.5

Bump version to 3.1.4

Bump version to 3.1.3

Bump version to 3.1.2

Bump version to 3.1.1

Bump version to 3.1.0

Bump version to 3.0.4