localtime() for win32 problem.

I found that localtime do not work same between linux and win32.

timet = -1000000; /* minus value */
localtime(&timet);

above codes do not work win32. (in Microsoft C, mingw gcc too)

so, score_timezone() function in src/timezone/pgtz.c should be changed. 
this problem is continuous with initdb when initdb run without setting TZ env value.