FTBFS on older arm

0.3.5.1-alpha failed to build on arm64/armhf/armel jessie, stretch (only arm64), trusty, xenial, and artful.

Looking at some of the logs, this comes up repeatedly:

src/lib/libtor-crypt-ops.a(src_lib_libtor_crypt_ops_a-aes_openssl.o): In function `aes_set_iv':
./build/../src/lib/crypt_ops/aes_openssl.c:399: undefined reference to `get_uint32'
./build/../src/lib/crypt_ops/aes_openssl.c:400: undefined reference to `get_uint32'
./build/../src/lib/crypt_ops/aes_openssl.c:401: undefined reference to `get_uint32'

https://jenkins.torproject.org/view/packages%20-%20debian/job/tor-debian-release-binaries-arm/44/

Cheers,