Function process_single_source_file() should return the trunit.

The index is already an in param. No need to return it.
Push all translation units into a list and dispose them before fini.
Fixed memleak of the display name of global variables.
Extended process_single_source_file() to accept command line args.
Removed all std:: qualifiers.

We are binding the std:: namespace globally in this file, so there is no
need to qualifier all kinds of identifiers with that namespace id.