This patch implemented the trans*.c part of allocatable scalar coarrays; 
contrary to noncoarray allocatable scalars, they have cobounds and thus 
use an array descriptor.

While there are still some bugs and minor omissions, gfortran slowly 
gets feature compile with regards to single-image coarrays support. 
Still to be done: Fixes to LOCK_TYPE constraint checks, polymorphic 
coarrays, some issues with coarray dummies, some issues with allocatable 
coarray components.

The patch also works with -fcoarray=lib. However, the to-do list for 
libcaf is much longer. On the front-end side, there are additional 
issues with argument passing, deallocate, some minor allocate issues 
("token"), and in particular calling the library for actual 
communication, for locking and for atomic access. Additionally, the 
message-processing loop in the library is still missing.

The attached patch was build and regtested on x86-64-linux.
OK for the trunk?

Tobias