Add a check for a specific config.sub/config.guess that causes errors for Android under MSYS/MingW.
Add a C++ wrapper for lo_version().
Add C++ wrappers for lo_timetag_now() and LO_TT_IMMEDIATE.
Add cpp_example to .gitignore.
Update version to 0.28 and update LO_SO_VERSION accordingly.

Two functions (lo_bundle_get_timestamp, lo_version) have been added
since 0.27, so 'current' gets a bump.