Fix typo in error message. (Bug 505774)

configure.in

@@ -7952,7 +7952,7 @@ if test "$NECKO_WIFI"; then
     if test "$ac_cv_header_iwlib_h" = "yes"; then
       NECKO_WIFI=1
     else
-      AC_MSG_ERROR([Can't find header iwlib.h for Necko WiFi scanning (might be in package iwlib-dev (Ubuntu) or wireless-tools-devel (Fedora)); use --disable-necko-wifi to disable])
+      AC_MSG_ERROR([Can't find header iwlib.h for Necko WiFi scanning (might be in package libiw-dev (Ubuntu) or wireless-tools-devel (Fedora)); use --disable-necko-wifi to disable])
     fi
   elif test "$OS_ARCH" = "Darwin"; then
     NECKO_WIFI=1