Doxygen docs

[Jeffrey Walton]

Hi Everyone/Tim,

This is from Wget2 master on Fedora 31. It looks like Doxygen.

If you are using Doxygen, then a nice option to detect Doxygen issues
is Clang's -Wdocumentation. Set CC=clang, and
CFLAGS="-Wdocumentation". It does a nice job of catching mistakes,
like missing parameters or undocumented parameters. I found it is a
little nicer then the doxygen tool.

Generating code for file wget.h...
/home/wget2/include/wget/wget.h:1499: warning: unable to resolve
reference to `wget_hpkp_db_free' for \ref command
/home/wget2/include/wget/wget.h:1503: warning: unable to resolve
reference to `wget_hpkp_db_free' for \ref command
/home/wget2/include/wget/wget.h:1505: warning: unable to resolve
reference to `wget_hpkp_db_check_pubkey' for \ref command
/home/wget2/include/wget/wget.h:1501: warning: unable to resolve
reference to `wget_hpkp_db_free' for \ref command
/home/wget2/include/wget/wget.h:1509: warning: unable to resolve
reference to `wget_hpkp_db_load' for \ref command
/home/wget2/include/wget/wget.h:1507: warning: unable to resolve
reference to `wget_hpkp_db_add' for \ref command
/home/wget2/include/wget/wget.h:1511: warning: unable to resolve
reference to `wget_hpkp_db_save' for \ref command