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

src/bacnet/datalink/crc.h

@@ -26,14 +26,17 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include "bacnet/bacnet_stack_exports.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif /* __cplusplus */
 
+    BACNET_STACK_EXPORT
     uint8_t CRC_Calc_Header(
         uint8_t dataValue,
         uint8_t crcValue);
+    BACNET_STACK_EXPORT
     uint16_t CRC_Calc_Data(
         uint8_t dataValue,
         uint16_t crcValue);