Since automake 1.12, the warnings in the category 'extra-portability'
are now enabled by '-Wall'. Because of this change, linking libtool
archives requires the new AM_PROG_AR macro.
For development snapshots, a 'devel' suffix is added to distinguish from
the final release. If necessary, the suffix can also be used for 'alpha'
and 'beta' releases.
When linking dynamically, the shared library contains a reference to all
external dependencies, and the linker can easily resolve them. However
when linking statically, all external dependencies have to be specified
explicitly. This rule also applies to dependencies that are not exposed
through the public api.
The pkg-config Requires.private field is used to support both static and
dynamic linking correctly.
