Add C++ guards to take care of C++ name-mangling.

The libfprint library is generally built with C calling conventions.
Which makes it difficult to link to C++ programs as it is.

This patch adds the support for linking with C++ code - by telling the C++
compiler to use C calling conventions for libfprint functions.

Reported-by: Guus Ellenkamp <guus@activediscovery.net>
Signed-off-by: Kunal Gangakhedkar <kunal.gangakhedkar@gmail.com>

libfprint/fprint.h

@@ -20,6 +20,10 @@
 #ifndef __FPRINT_H__
 #define __FPRINT_H__
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <stdint.h>
 #include <sys/time.h>
 
@@ -336,5 +340,9 @@ typedef void (*fp_identify_stop_cb)(struct fp_dev *dev, void *user_data);
 int fp_async_identify_stop(struct fp_dev *dev, fp_identify_stop_cb callback,
 	void *user_data);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif