Fail the configure script when Fortran 2003 interface is requested but the compiler does not support CHARACTER interoperability.

Give the compiler a chance to clean its temporary files when requesting its version at the configure time.

* Versions 4.1 to 4.3.2 of netcdf do not provide programmatically useful
  pre-processor predicate if the pnetcdf layer is available and report
  success when the nc_create call actually failed.

* Also intercept nc__enddef for parallel access.

* And fallback to serial if not. Unfortunately this can only be queried at
  run-time it seems.

* And add corresponding check to test suite.

* 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.

This reverts commit de09e3fb.

* This function will then be used by lazy netcdf implementation to map
  a page of inaccessible memory.

* The original test did not work for clang.