share stored predicates

share stored predicates

while most of the duplication in predicates was caused by stubs,
this is still a 5% win on libcore.

567924 liballoc-bb943c5a.rlib
1425564 liballoc_jemalloc-bb943c5a.rlib
10520 liballoc_system-bb943c5a.rlib
154842 libarena-bb943c5a.rlib
4113790 libcollections-bb943c5a.rlib
18513674 libcore-bb943c5a.rlib
199466 libflate-bb943c5a.rlib
249548 libfmt_macros-bb943c5a.rlib
560488 libgetopts-bb943c5a.rlib
226772 libgraphviz-bb943c5a.rlib
442966 liblibc-bb943c5a.rlib
189884 liblog-bb943c5a.rlib
736764 librand-bb943c5a.rlib
609874 librbml-bb943c5a.rlib
1411678 librustc_back-bb943c5a.rlib
38770354 librustc-bb943c5a.rlib
12868 librustc_bitflags-bb943c5a.rlib
2327196 librustc_borrowck-bb943c5a.rlib
582178 librustc_data_structures-bb943c5a.rlib
9379344 librustc_driver-bb943c5a.rlib
9540324 librustc_front-bb943c5a.rlib
1614996 librustc_lint-bb943c5a.rlib
79217876 librustc_llvm-bb943c5a.rlib
4833518 librustc_mir-bb943c5a.rlib
3535794 librustc_platform_intrinsics-bb943c5a.rlib
603190 librustc_privacy-bb943c5a.rlib
3158032 librustc_resolve-bb943c5a.rlib
14300126 librustc_trans-bb943c5a.rlib
12024054 librustc_typeck-bb943c5a.rlib
1834852 librustc_unicode-bb943c5a.rlib
15611582 librustdoc-bb943c5a.rlib
2926594 libserialize-bb943c5a.rlib
8780060 libstd-bb943c5a.rlib
30772000 libsyntax-bb943c5a.rlib
917984 libterm-bb943c5a.rlib
1369754 libtest-bb943c5a.rlib