Fortran: set version field in CFI_cdesc_t to CFI_VERSION

Fortran: set version field in CFI_cdesc_t to CFI_VERSION

When converting a GFC descriptor to a CFI descriptor, it was
incorrectly copying the version number from the former to the latter.
It should be using the value of CFI_VERSION instead (currently 1).
Going the other direction, the GFC version field is initialized to
zero elsewhere, so do that here too.

2021-06-30  Tobias Burnus  <tobias@codesourcery.com>
	    Sandra Loosemore  <sandra@codesourcery.com>

	libgfortran/
	* runtime/ISO_Fortran_binding.c (cfi_desc_to_gfc_desc):
	Initialize version field to 0.
	(gfc_desc_to_cfi_desc): Initialize version field to CFI_VERSION.