libbb: remove vdprintf

Two reasons:

* it's only built for GNU C Library versions < 2 (released 1997)

* it isn't used anywhere in BusyBox

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

include/libbb.h

@@ -167,9 +167,6 @@
 /* Some libc's forget to declare these, do it ourself */
 
 extern char **environ;
-#if defined(__GLIBC__) && __GLIBC__ < 2
-int vdprintf(int d, const char *format, va_list ap);
-#endif
 /* klogctl is in libc's klog.h, but we cheat and not #include that */
 int klogctl(int type, char *b, int len);
 #ifndef PATH_MAX