Hi, This patch series fixes an issue with `const_double_zero' use causing a build failure reported with the `pdp11-aout' target by Martin Liška: <https://gcc.gnu.org/pipermail/gcc-patches/2020-December/561896.html> superseding an earlier proposal discussed here: <https://gcc.gnu.org/pipermail/gcc-patches/2020-December/561972.html>.
I have decided to split the fix into pieces so as to have targets bits as separate changes in order to make possible backports easier. In the course of investigation I have noticed a VAX iterator attribute I have recently introduced duplicates the standard `mode' attribute unnecessarily so I have decided to remove it along with the fix; it has a syntactic dependency on 3/4, so it has to be a part of the series. See individual changes for detailed descriptions. These changes have been regression-tested with the `vax-netbsdelf' target and verified manually with the `pdp11-aout' target. For 4/4 I have also verified that no change has been made to target library code produced. OK to apply? Maciej
