Patch for mocassin to fix FTBFS with gcc-10

[Roger Wesson <rw@nebulousresearch.org>]

Hi,

My package mocassin failed to build with GCC-10 due to some rank and 
type mismatches no longer being tolerated (details are in 
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=957555). Pending a 
proper fix upstream, I have updated the package to compile with 
"-std=legacy" so that these mismatches are still tolerated. Can the new 
package be uploaded, assuming that's ok and a reasonable way to deal 
with the issue? If there are better ways to address this I'd be glad to 
implement them.

Cheers,
Roger