Added new option 'static' for yaz-config which makes 'yaz-config --libs'

Added new option 'static' for yaz-config which makes 'yaz-config --libs'
returns static libs rather than shared libs for in-source compilations.
This is to make Pazpar2 work for local builds when YAZ is built
both statically and with shared objects. We have not seen this problem
before because most other applications are built with Libtool. And
these that aren't, such as PHP / Perl extensions deal with shared
objects fine.