* Since write, mmap and a number of other functions are not part of
  ISO C (i.e. strictly conforming programs must not use those), we need
  to ensure the build environment provides POSIX conformance.
* This mostly prevents unrelated bug reports later on.
* From POSIX 2008, CDI unconditionally only uses getline and has a
  work-around in case that is missing.

* Also automatically find cfortran.h flag for as many platforms as we
  can test at the moment.

* r3363: merged changes from branches/cdi_fileDrivenInput

* This way the MPI parts of CDI can be compiled without introducing
  an artificial MPI dependency for non-MPI parts.

* Add proper formatting of example program output.
* Add test to ensure the examples are working.
* Add better handling of Pointer arguments.
* Add better handling of C char * return values.
* Add helper function for C character length.
* Test that the compiler properly support Fortran/C interop at configure
  time.

* This way it could be used in out-of-source builds with some modifications.

* This also adds separate documentation, header, Fortran wrappers and
  pkg-config file for the cdi-pio part of the library

* The added pkg.m4 accounts for pkg.m4 sometimes not being available or
  having another version.

* If these are set they already override the corresponding variable.
* Also reduce number of spurious linefeeds in configure.