New patches submitted from eg123 for the automatization of
the configuration process.
Use of pkg-config to find dolfin and eigen3 includes and libs
* src/Makefile.in: make variables (CPPFLAGS, LDFLAGS, LIBS)
are defined substituting the Autoconf ones
* src/configure.ac: dolfin and eigen3 compile and link flags
are looked for through pkg-config macros
* DESCRIPTION: added pkg-config as a build-dependency