Update ancillary mono ports

x11-toolkits/gnome-sharp20:

• update to version 2.24.4
• use github for sources
• use autoreconf and provided bootstrap script (pre-configure)
• remove gettext-runtime, not used by port
• order USES section, move non-USES related variables to own section

x11-toolkits/gtk-sharp20:

• update to version 2.12.45
• remove gettext-runtime, not used by port
• order USES section, move non-USES related variables to own section

Differential Revision: https://reviews.freebsd.org/D13751