net/fort: don't depend on gcc10, fix version check
The current version of FORT builds fine with any c11 compiler. There is
no need for USE_GCC.
Patch the build system to correctly define the version of FORT as seen
in the output of "fort --version" and the "User-Agent:" HTTP header. 
Approved by: Toni Yannick Kalombo <firstname.lastname@example.org> (maintainer)
Reported by: Mark Tinka <email@example.com>