* Removed -lpthread from xmlrpc.m4 generation of XMLRPC_LIBS - newer gcc linker faults if -lpthread is out of order
Don't try to run xmlrpc-c-config when building without xmlrpc support
Simplify pkg-config.m4 and make sure that pkg-config can be overridden by setting CFLAGS & LIBS variables. Likewise for xmlrpc.m4. Also add static switches around xmlrpc linker flags when --enable-static has been specified.