Update to 1.6.99.3
Changes:

• list of valid url scheme can be defined in pkg.conf
• add support for SOURCE_DATE_EPOCH for reproducible builds
• Fix pkg check -d
• Fix testsuite with kyua 0.12
• Fix pkg info -R
• Fix setting modes on extracted files/directories
• Fix zsh completion for pkg info -l
• Fix some solver crashed
• Initial attempt at fixing infinite loop on multirepositorry when updating pkg
• pkg version now handled -q correctly