Remove Time argument from xsetsel

This is an X type and should be internal to x.c.

The selcopy() function was a single line and only used in one place, so
it was inlined to reduce LOC.

Signed-off-by: Devin J. Pohly <djpohly@gmail.com>

win.h

@@ -16,4 +16,4 @@ int xsetcolorname(int, const char *);
 void xsettitle(char *);
 int xsetcursor(int);
 void xsetpointermotion(int);
-void xsetsel(char *, Time);
+void xsetsel(char *);