Update external function definitions in the compiler

[Martin Sjölund]

All external functions in Compiler/*.mo need to be updated to avoid name clashes.
{{{public function time

output Real outReal;

• external "C";

+ external "C" outReal=System_time() annotation(Library = "omcruntime");
end time;}}}

After that, they also need to be implemented in omcruntime (see the attachment)

[Martin Sjölund]

Missing function definitions for the linker

[Martin Sjölund]

Resolved. We can now compile Main_main and run the bootstrapped OMC.