The `HYPERROGUE_USE_ROGUEVIZ=1` build now uses inline variables.
So we pass `-std=c++17` in the Makefile. But GCC 5.4.0 (Travis's
default system compiler on Ubuntu Xenial) doesn't recognize
inline variables even in `-std=c++17` mode. Therefore, we must
pass `dist: bionic` to Travis, to get it to use Ubuntu Bionic,
whose system compiler is GCC 7.4.0. But we do this only for the
one entry in the build matrix that builds RogueViz with GCC
on Linux. Nobody else needs `dist: bionic`.
The bug was that my hack to support `g++-5` accidentally prevented
Travis from ever using `clang++`! So all our "Clang" builds were quietly
using regular `g++` instead. This is now fixed, and in fact I've removed
the `g++-5` build because its GCC 5.5.0 is not significantly different
from the regular `g++` build's GCC 5.4.0.
Also, add two more configurations to the build matrix.
Since `HYPERROGUE_USE_ROGUEVIZ=1` now uses `-std=c++17`, we want to
make sure that we run builds on every platform both with `HYPERROGUE_USE_ROGUEVIZ=1`
(to prove that the RogueViz code compiles) and without (to prove that
the non-RogueViz code still compiles as `-std=c++11`).
If a translation file contains two copies of the same English string,
with the same translation, then we don't care at all; just throw out
the second copy.
If a translation file contains two copies of the same English string,
with DIFFERENT translations, then (according to how the game does
translation) one of those translations must be inappropriate. Give
a warning in that case; and again, throw out the second copy because
we are forced to pick ONE translation for use within the game.
Also fix some minor typos I noticed in the strings.
