Use %x when printing the TID

Use %x when printing the TID

One spot in windows-nat.c uses %ld to print the TID, but all other
spots use %x, as does the infrun logging.  This makes it unnecessarily
hard to tell which other log messages correspond to this one.  This
patch changes the one outlier to use %x.

gdb/ChangeLog
2019-10-15  Tom Tromey  <tromey@adacore.com>

	* windows-nat.c (windows_nat_target::resume): Use %x when logging
	TID.

Change-Id: Ic66efeb8a7ec08e7fb007320318f51acbf976734