Remove rust_run_program.cpp

Some of the functions could be converted to rust, but the functions dealing with
signals were moved to rust_builtin.cpp instead (no reason to keep the original
file around for one function).

Closes #2674
auto merge of #9280 : alexcrichton/rust/less-c++, r=brson

Some of the functions could be converted to rust, but the functions dealing with
signals were moved to rust_builtin.cpp instead (no reason to keep the original
file around for one function).

Closes #2674

Because less C++ is better C++!