Removed extraneous HUHU.

This implements an idea that Nicolas had to overcome the Darwin
problem that it is not possible to extend a shared memory segment
on that system.

The remedy is simple: Use a memory segment that is larger than
what can reasonably be used. This should only waste a few page
table entries, while providing the functionality, at least for
further testing.

libgfortran/ChangeLog:

	* caf_shared/shared_memory.c (shared_memory_init): On Apple,
	use an initial size of 256 GB.

libgfortran/ChangeLog:

	* caf_shared/README.native_coarrays: Remove atomics from list
	of unsupported features.

After the discussions about PTHREAD_PROCESS_SHARED and after
observing that on Cygwin the program simply hangs because
this flag is not implemented there, the best way is to check
for errors and exit with a clear error message instead of
some mysterious hang.

libgfortran/ChangeLog:

	* caf_shared/util.c (ERRCHECK): New macro.
	(initialize_shared_mutex): Use it to check return codes.
	(initialize_shared_condition): Likewise.

gcc/fortran/ChangeLog:

	* trans-array.c (gfc_conv_ss_descriptor): Use correct ref.
	* trans-intrinsic.c (trans_argument): Use gfc_conv_expr_reference.
	* trans-decl.c (gfc_build_builtin_function_decls):
	Correct spec for array.

libgfortran/ChangeLog:

	* caf_shared/collective_subroutine.c (collsub_reduce_array):
	Fix off by one error for result.

gcc/testsuite/ChangeLog:

	* gfortran.dg/caf-shared/co_reduce_1.f90: New test.