String literals in C++ are implicitly typed as 'const char *', and with
this change, their const-ness is maintained when assigning them to
variables or passing them as arguments. This significantly cuts down the
number of warnings generated by the compiler.
little test app that links against it. I still need to polish a few
things, but this is more or less as it should be.
[git-p4: depot-paths = "//depot/solvespace/": change = 1944]