Signedness of fortran size_type_node

[Zdenek Dvorak]

Hello,

I have just noticed that size_type_node is signed in fortran frontend
(it caused an ice for me because unsigned_type_for returns it for
pointers, and I inserted an assert that the result of unsigned_type_for
is unsigned).

According to the comment in tree.h, size_type_node should correspond to
"The C type `size_t'", and standard specifies that size_t is unsigned.

Is this a bug in fortran frontend, or is size_type_node intentionally
set in a different way?

Zdenek