The ssl useflag was masked for pan when gnutls-3 was not released for stable arches. These days gnutls-3 is stable, so this useflag can be unmasked again. Thank you.
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=584ba4d39e78bdf2d2977af5656e1bc038036499
Perfect. Thank you Pacho.