Update devel/cmake* to 3.7.1 [1]

Due to an upstream commit [2] we need now to pass
CMAKE_INSTALL_MANDIR:PATH="share/man" in the
devel/llvm-* ports, and fix the plist of net/remmina.
Further add an upstream patch to math/plplot to
fix the build with 3.7.1.

[1] https://cmake.org/cmake/help/v3.7/release/3.7.html
[2] https://github.com/kitware/cmake/commit/956054

PR: 214975
Approved by: rakuco (mentor)
Exp-run by: antoine