Improve gnulib in gdb's guess work, gettimeofday() works in uClibcm promise.

This patch helps building x86_64-unknown-linux-uclibc toolchains, the final
gdb-native step otherwise fails when linking the libinproctrace.so

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

--- a/gdb/gnulib/configure	2016-02-25 18:17:04.145903807 +0100
+++ b/gdb/gnulib/configure	2016-02-25 18:17:28.545903821 +0100
@@ -13520,8 +13520,9 @@
   if test "$cross_compiling" = yes; then :
   # When cross-compiling:
       case "$host_os" in
-                # Guess all is fine on glibc systems.
+                # Guess all is fine on glibc/uclibc systems.
         *-gnu*) gl_cv_func_gettimeofday_clobber="guessing no" ;;
+        *-uclibc*) gl_cv_func_gettimeofday_clobber="guessing no" ;;
                 # If we don't know, assume the worst.
         *)      gl_cv_func_gettimeofday_clobber="guessing yes" ;;
       esac