* libhppa.h (PA_PAGESIZE): Define.

    * libhppa.h (PA_PAGESIZE): Define.

        * som.c (SOM_ALIGN): Define.
        (som_begin_writing): If writing an executable, initialize all
        fields in the exec header to zero.  Update fields in the exec
        header as sizes of loadable subspaces are computed.  Carefully
        preserve alignments when building executables.  Actually write the
        exec after all the fields are filled in.