RUST global variables do not appear on the left panel

[phelluy]

When you have global variables in a Rust source file, functions, modules, etc. appear in the left panel. However, the global variables do not appear. This functionnality works well in C and C++. It would be nice if it worked also for Rust.

Minimal example:

The global variable "N" does not appear in the left panel

[elextr]

Depends on ctgas parser, might improve when #2666 is merged.