libzrtp: add bootstrap script

libs/libzrtp/projects/gnu/autoreconf.sh

-#!/bin/bash
-aclocal -I ./config/
-autoheader
-autoconf
-automake

libs/libzrtp/projects/gnu/bootstrap.sh

+#!/bin/bash
+
+reconf () {
+  aclocal
+  libtoolize --copy --automake
+  autoconf
+  autoheader
+  automake --no-force --add-missing --copy
+}
+
+(cd ../../third_party/bnlib && reconf)
+reconf
+