Add two switches -a and -g to control the antialiasing bits for
text and graphics, respectively.
* src/devices/grohtml/post-html.cc (main): Dummy code for `-a' and
`-g'.
* src/devices/grohtml/grohtml.man: Document them.
* src/preproc/html/pre-html.cc (MIN_ALPHA_BITS, MAX_ALPHA_BITS):
New macros.
(textAlphaBits, graphicAlphaBits, antiAlias): New global variables.
(setupAntiAlias): New function.
(createAllPages): Updated.
(scanArguments): Handle `-a' and `-g'.
(main): Call `setupAntiAlias'.
* NEWS: Updated.
* doc/groff.texinfo (Def*): Call index function after deffn.
* tmac/html.tmac: Call `nroff' request.