icpc compiles happy on MacOSX both with -xCOMMON-AV512 and native AVX
gcc-5 does not compile happy; can work around by renaming lattice peek/poke/transpose/trace templates
relative to tensor ones, but gcc goes into a recursive template instantiation due to
matching error. I think this is a gcc bug and have filed a report https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66153
