- handle HTML tagging via (client-installable) Stylers

go/doc:
- basic styler support
- some factoring
- ready to contain the search code (but for now excluded)

doc/style.css:
- updated

doc/go_spec.css:
- cleanup: replace deprecated uses of <font> tag with <span> tag

R=rsc
DELTA=302  (160 added, 62 deleted, 80 changed)
OCL=35973
CL=35996