Source changes needed for Microsoft Visual C++ compatibility.
Includes an implementation of strptime, compiled only for Win32 platform.
Corrected filename for strptime.cc
Additional changes required for MSVC to compile ledger.
These changes only matter if ledger is compiled with USE_PYTHON.
Merge pull request #195 from code-affinity/msvc-11.0

Minor source code changes required to compile with Microsoft Visual C++ 11 (2012)