FWIW this is not specific to the Windows help, but applies also to gnuplot.gih, gnuplot's text-based help system. Many (none?) of the two-letter acronyms like "pt", "ps", "dt", "lc, "lt", "lw" seem to be indexed.
mingw/woa: fix installation of demo files
Colons need to be entered as tags for the OS/2 help
Test for ioctl.h header is not sufficient
os2: enforce C99 with old compilers and extend inttypes
os2: sync with configure.hin
djgpp: fix demo binary files and change defaults
djgpp: sync with configure.hin