Continue to refactor arg.cpp

Simple cleanup. No changes in functionality.

Major observable is to split process_args() into two functions
  - The loop over the Environment variables
  - The loop over the Command Line



Compiled:   STD on clang    STD/LLVM on gcc

Tested:     Ran some test cases of setting up the command line
            paratest

Reviewed:   None




git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23616 3a8e244f-b0f2-452b-bcba-4c88e055c3ca