Add back Darwin/Mach/Apple portability

Quite a few of the changes against the MalcolmRobb/dump1090 fork are
incompatible with OSX.  This patch adds back that cross platform support
back.

.travis.yml

@@ -1,9 +1,23 @@
 language: c
 
+os:
+    - linux
+    - osx
+
 before_install:
-  - sudo add-apt-repository ppa:gqrx/releases -y
-  - sudo apt-get update -qq
-  - sudo apt-get install -y build-essential debhelper librtlsdr-dev libusb-1.0-0-dev pkg-config
+    - if [ `uname` = "Linux" ]; then
+          sudo add-apt-repository ppa:gqrx/releases -y;
+          sudo apt-get update -qq;
+          sudo apt-get install -y build-essential debhelper librtlsdr-dev libusb-1.0-0-dev pkg-config;
+      elif [ `uname` = "Darwin" ]; then
+          brew update;
+          brew install -v librtlsdr;
+      fi
 
 script:
-  - dpkg-buildpackage -b -us -uc
+    - if [ `uname` = "Linux" ]; then
+          dpkg-buildpackage -b -us -uc;
+      elif [ `uname` = "Darwin" ]; then
+          make;
+         make test;
+      fi