Add support for Workgroup 4 (WG4) channel mapping

This is the channel ordering used in DVD Audio, and is the standard
used internally in the VLC media player.
Allow setting bitrate modes 1-5 too

These correspond to different VBR modes.
Add automake/autoconf source files

Also add examples.
Avoid casting arbitrary values to an enum

The enum only contains the constant values 0, 1 and 2. This produces
the warning "comparison of constant 6 with expression of type
'PS_RESOLUTION' is always false" in clang for the first check
in the getNoBands function (but apparently not for the second one
even though mode>=3 shouldn't ever happen for a valid PS_RESOLUTION
value either). This could allow the compiler to completely remove
the conditions that shouldn't be able to occur even though they
actually are used and are necessary.

By passing the value as UINT instead, it is clear to the compiler
that all the checks are necessary.
Include the encoder library version in the publicly installed header

This allows callers to conditionally use new API features without
breaking compatibility with the earlier versions of the library.