Code clean-up for new compilers.
The 'kwset' one may get a wholesale replacement, either with new
version of kwset from upstream or removal of its users, but in the
meantime, it is probably OK to merge it down.
* js/gcc-8-and-9:
config: avoid calling `labs()` on too-large data type
winansi: simplify loading the GetCurrentConsoleFontEx() function
kwset: allow building with GCC 8
poll (mingw): allow compiling with GCC 8 and DEVELOPER=1