Fix debug output in the dynamic linker.

This provides a mini-printf implementation that reduces the
size of the dynamic linker by 25 KB, by preventing the drag of
formatting-related routines from the C library.

Also allow traces to be sent to the log, instead of stdout.

NOTE: You now need to modify Android.mk to enable/disable debug
      output.

linker/dlfcn.c

@@ -17,6 +17,7 @@
 #include <pthread.h>
 #include <stdio.h>
 #include "linker.h"
+#include "linker_format.h"
 
 /* This file hijacks the symbols stubbed out in libdl.so. */
 
@@ -45,7 +46,7 @@ static pthread_mutex_t dl_lock = PTHREAD_MUTEX_INITIALIZER;
 
 static void set_dlerror(int err)
 {
-    snprintf(dl_err_buf, sizeof(dl_err_buf), "%s: %s", dl_errors[err],
+    format_buffer(dl_err_buf, sizeof(dl_err_buf), "%s: %s", dl_errors[err],
              linker_get_error());
     dl_err_str = (const char *)&dl_err_buf[0];
 };