lang/mono: update to 4.6.1.5.

USES=mono: add nuget argument

The nuget argument adds support for nuget packages.  The nuget
packages must be specified in the NUGET_DEPENDS variable.

devel/monodevelop: update to 6.1.1.15

• Switch to github. The other official source is quite a few versions behind.
• Add missing dependencies (fsharp, ssl2, curl)
• Add required nuget packages
• Add required external repositories
• Drop options. Although ./configure offers these flags, there is no functional change (i.e. no-op)
• All patches have been upstreamed (and the one we need is from upstream).

lang/fsharp: update to 4.0.1.15

• convert to use the nuget argument.
  
  ChangeLog:
  • Fix null condition in Fsc task

lang/mono-devel: update to 4.6

• switch to new test target (currently tests the port to be installed)

www/gecko-sharp20: depreciate: broken and no-upstream

• Give 1 month for anyone to complain that this port is being removed.

x11-toolkits/gtk-sharp30: bump PORTREVISION

• Add LICENSE information
• Add missing dependencies (per stage-qa)

x11-toolkits/gtk-sharp20: update to 2.12.40.

• Add LICENSE information
• Add missing dependencies (per stage-qa)
• Change download location per Mono's Gtk# website.

PR: 213484
PR: 213796
Reviewed by: mat, romain
Differential Revision: https://reviews.freebsd.org/D8339