[boost] [thread] r62122 fix for #3178 introduces duplicate symbol

Hi list. In trunk, revision 62122 (which fixes a negative sleeping time bug #3178) added a detail helper function pin_to_zero at boost/thread/win32/thread_data.hpp:148, which isn't marked inline. This leads to multiple symbol definitions for anything that tries to link to Boost.Thread. The fix is trivial, just add an inline. -- Lars Viklund | zao@acc.umu.se