fix for process_tests.cpp compilation

MSVS2012/WinSDK 8.0/CMake/Target 64bit

process_tests.cpp failed to compile with following error

21>  process_tests.cpp
21>C:\WORK\GITHUB\pion\include\pion/test/unit_test.hpp(57): warning C4100: 'test_cases_amount' : unreferenced formal parameter
21>C:\WORK\GITHUB\pion\include\pion/test/unit_test.hpp(253): warning C4267: 'initializing' : conversion from 'size_t' to 'long', possible loss of data
21>C:\Program Files (x86)\Windows Kits\8.0\Include\um\DbgHelp.h(77): error C2146: syntax error : missing ';' before identifier 'ModuleName'
21>C:\Program Files (x86)\Windows Kits\8.0\Include\um\DbgHelp.h(77): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
21>C:\Program Files (x86)\Windows Kits\8.0\Include\um\DbgHelp.h(78): error C2146: syntax error : missing ';' before identifier 'hFile'
21>C:\Program Files (x86)\Windows Kits\8.0\Include\um\DbgHelp.h(78): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
21>C:\Program Files (x86)\Windows Kits\8.0\Include\um\DbgHelp.h(79): error C2146: syntax error : missing ';' before identifier 'MappedAddress'

This because for project with tests windows.h was not included before dbghelp.h in process.hpp

So my proposal is put it in common .hpp file.