Export symbols in order to support shared libraries (#54)

* Add BAC_ROUTING compile definition

* Reorder cmake

* Fix OpenSSL support: support both 1.0 and 1.1t pus

* Explicitly export symbols, hidden by default

* Build shared libraries on travis using cmake

* Learn Makefile about static library

* Fix build using mingw with cmake

* Do not cleanup twice or after potential free

.travis.yml

@@ -22,7 +22,7 @@ jobs:
     - stage: demos-build-cmake
       os: linux
       compiler: gcc
-      script: mkdir build && cd build && cmake .. && cmake --build . --clean-first
+      script: mkdir build && cd build && cmake .. -DBUILD_SHARED_LIBS=ON && cmake --build . --clean-first
     - stage: gateway-build
       os: linux
       compiler: gcc