Remove hack for mingw compiler.

The __BEGIN_DECLS/__END_DECLS macro is now defined for mingw.

Change-Id: Icd09b92a83e982ac0ed3eb34df4c1d79de21941e
diff --git a/include/backtrace/backtrace.h b/include/backtrace/backtrace.h
index d76affa..8a45690 100644
--- a/include/backtrace/backtrace.h
+++ b/include/backtrace/backtrace.h
@@ -21,13 +21,7 @@
 #include <stdbool.h>
 #include <sys/types.h>
 
-#ifdef USE_MINGW
-#if defined(__cplusplus)
-extern "C" {
-#endif  // defined(__cplusplus)
-#else
 __BEGIN_DECLS
-#endif  // USE_MINGW
 
 // When the pid to be traced is set to this value, then trace the current
 // process. If the tid value is not BACKTRACE_NO_TID, then the specified
@@ -123,12 +117,6 @@
 /* Get the backtrace data structure associated with the context. */
 const backtrace_t* backtrace_get_data(backtrace_context_t* context);
 
-#ifdef USE_MINGW
-#if defined(__cplusplus)
-}
-#endif  // defined(__cplusplus)
-#else
 __END_DECLS
-#endif  // USE_MINGW
 
 #endif /* _BACKTRACE_H */