[tree-ssa] Add missing GTY

[law@redhat.com]

In message <hovfzpfiqw.fsf@byrd.suse.de>, Andreas Jaeger writes:
 >
 >With the appended patch, bootstrap come a bit further on the tree-ssa
 >branch.
 >
 >It now stops with:
 >/usr/src/aj/cvs/gcc-tree-ssa-20020619-branch/gcc/tree-dfa.c: In function `dum
 >p_alias_info':
 >/usr/src/aj/cvs/gcc-tree-ssa-20020619-branch/gcc/tree-dfa.c:1922: warning: in
 >t format, different type arg (arg 4)
 >
 >I'll fix this tomorrow but let's first solve this issue.
 >
 >Ok to commit?
 >
 >Andreas
 >
 >2003-02-12  Daniel Berlin <dberlin@dberlin.org>
 >            Andreas Jaeger  <aj@suse.de>
 >
 >	* tree-flow.h: At some garbage collector marks.
Approved.
jeff