At present, the only way to get the full libg++ documentation, including IOstream (which is currently missing from the web version of the documentation), is as follows:
setenv INFOPATH ${INFOPATH}:/vol/vssp/vap/soft/GNU/info:/vol/vssp/packages.sun4/GnuCompilers/info
<CTRL>H <CTRL>I libg++ <RET>
This will take you into the emacs "info" hypertext system at the libg++ page.