python: add wrapper code for ITT-NERSC implementation to ensure compatibility

[mk-srivastava]

In the NERSC implementation of ITT API(Link), there are 9 functions.

Each of the function is listed below with the description about the changes done to support them.

1. resume : Have used the existing resume implementation in ittapi.
2. pause : Have used the existing pause implementation in ittapi.
3. detach : Have used the existing detach implementation in ittapi.
4. domain_create : Have used the existing domain implementation in ittapi and renamed it as domain_create.
5. task_begin : This function is same as the task_begin implementation in ittapi, so have used that API function directly with only change that in ittapi, in task_begin is expected to have task name in StringHandle format. So, this change is done and existing API is used afterward.
6. task_end : This function is same as the task_end implementation in ittapi, so have used that API function directly.
7. pt_region_create : pt_region is one of things that's not there ittapi implementation. So, to support this, a new structure to handle pt_region is created along with utility functions to handle them in [pt_region.hpp, pt_region.cpp]. As a new structure is created so listed that at [ittapi.cpp]
8. pt_region_begin : This python function is binded to C function pt_region_begin which in turn is implemented in [pt_region.cpp].
9. pt_region_end : This python function is binded to C function pt_region_end which in turn is implemented in [pt_region.cpp].

A separate module ittapi.compat for NERSC implementation is created, thus the folder ittapi/compat/ and ittapi/compat/__init__.py listing all the supported functions by the module.

To include and build the newly created cpp file pt_region.cpp, setup.py is changed.

Rest of the changes are to add the unit test cases for the module ittapi.compat added.

[oleksandr-pavlyk]

ittapi.compat module is a great idea. I should perhaps reference it from itt-python README file.

I left some suggested edits, mostly nits.