Finished initial uart code, it compiles.
The next task is writting unit tests for it.
Also fixed some minor issues in Brian's code.
Finally, fixed a minor problem in download_externals.sh
that was causing things not to build properly.
diff --git a/aos/build/download_externals.sh b/aos/build/download_externals.sh
index f33eced..9d8a9f5 100755
--- a/aos/build/download_externals.sh
+++ b/aos/build/download_externals.sh
@@ -153,7 +153,7 @@
GMP_DIR=${COMPILED}/gmp-${GMP_VERSION}
GMP_PREFIX=${GMP_DIR}-prefix
GMP_LIB=${GMP_PREFIX}/lib/libgmp.a
-GMP_URL=http://ftp.gmplib.org/gmp/gmp-${GMP_VERSION}.tar.lz
+GMP_URL=ftp://ftp.gmplib.org/pub/gmp/gmp-${GMP_VERSION}.tar.lz
[ -f ${GMP_TAR} ] || wget ${GMP_URL} -O ${GMP_TAR}
[ -d ${GMP_DIR} ] || ( mkdir ${GMP_DIR} && tar \
--strip-components=1 -C ${GMP_DIR} -xf ${GMP_TAR} )