malloc(9): update names and hardlinks

[mhorne]

Summary

Give all documented functions a .Nm entry in the man page, following the
order they are listed in the synopsis. Create MLINKs for each of the
functions as well.

While here, add a missing include directive to the synopsis, and appease
mandoc by wrapping a long line.

[mhorne]

There are a few additional functions listed in the man page that don't have MLINKS: malloc_usable_size(), malloc_aligned(), malloc_exec(), malloc_domainset_exec(). zfree() is more widely used than these others.

[markj]

I think it's fine to hardlink all of the functions you mentioned...

[jhb]

Agree with Mark on linking them all.

[imp]

mark is quite sensible in the advise he gives. I agree.

[mhorne]

Add more MLINK entries, and .Nm entries as well.