Fixed windows-specific warning about undeclared localtime_r() in my_time.c.

We have to include my_pthread.h since it is the place where localtime_r() is declared 
on platforms where this function is missing.

sql-common/my_time.c

@@ -17,6 +17,8 @@
 #include <my_time.h>
 #include <m_string.h>
 #include <m_ctype.h>
+/* Windows version of localtime_r() is declared in my_ptrhead.h */
+#include <my_pthread.h>
 
 ulonglong log_10_int[20]=
 {