enhance support for validating a call stack for the main thread of a process. specifically, handle the case where an executable uses a main provided by  a dynamically-linked shared library.
enhance support for validating a call stack for the main thread of a process.
specifically, handle the case where an executable uses a main provided by 
a dynamically-linked shared library.

zcth428/hpctoolkit111,zcth428/hpctoolkit111,zcth428/hpctoolkit111,zcth428/hpctoolkit111,zcth428/hpctoolkit111