Another pass on cleaning up the command line processor

1) Altered the typedef for ArgumentFunction so that the
ArgumentState variable is const

2) Propagated this change through log.{h,cpp} and multiple
points in driver.cpp

3) Small changes to the control flow in arg.cpp to simplify
the business logic.


Compiled: STD on clang
          STD/LLVM on gcc

Tested:   Paratest

Reviewed: None





git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23665 3a8e244f-b0f2-452b-bcba-4c88e055c3ca