a56: Add missing prototypes for alloc() and fixstring()

a56: Add missing prototypes for alloc() and fixstring()

This patch is incorporated from the Debian version of the package.
There is a note that the Debian packaging is licensed under the GPL
version 3 (or any later version.) While it may have been intended
that only the Debian "packaging" falls under the GPLv3 (based on the
wording) and not changes to the program code it calls out nothing
separate for the patches, which are also contained in the Debian
packaging, and so I am treating them as if the patches are also under
the GPLv3+ and not the program's own license since that is the only
permission statement available.