build: rewrite most of configure using new macros

build: rewrite most of configure using new macros

Most of the checks are now a single macro call, making the configure
script much easier to read.

The use of --enable and --with flags has been streamlined.  Optional
libraries use --with-foo, some of them accepting the value 'dyn' to
activate runtime dynamic loading.  The optional formats use --enable,
again with the value 'dyn' enabling dynamic loading.

As before, the default behaviour is to detect libraries and enable
support for available ones.  If an explicitly enabled feature has a
dependency that is missing or disabled, an error is reported.