implement wprintf family of functions

this implementation is extremely ugly and inefficient, but it avoids a
good deal of code duplication and bloat. it may be cleaned up later to
eliminate the remaining code duplication and some of the warts, but i
don't really care about its performance.

note that swprintf is not yet implemented.

src/stdio/vwprintf.c

@@ -0,0 +1,7 @@
+#include <stdio.h>
+#include <wchar.h>
+
+int vwprintf(const wchar_t *fmt, va_list ap)
+{
+	return vfwprintf(stdout, fmt, ap);
+}