Fix visibility issues under (mostly on win32)

Refs: libevent#511
Fixes: 7182c2f ("cmake: build SHARED and
STATIC libraries (like autoconf does)")

(cherry picked from commit ce3af53)

Author: azat

include/event2/visibility.h

@@ -40,25 +40,15 @@
 # elif defined __GNUC__
 #  define EVENT2_EXPORT_SYMBOL __attribute__ ((visibility("default")))
 # elif defined(_MSC_VER)
-#  define EVENT2_EXPORT_SYMBOL extern __declspec(dllexport)
+#  define EVENT2_EXPORT_SYMBOL __declspec(dllexport)
 # else
 #  define EVENT2_EXPORT_SYMBOL /* unknown compiler */
 # endif
 
 #else /* event_*_EXPORTS */
 
-# if defined(_MSC_VER)
-#  define EVENT2_EXPORT_SYMBOL extern __declspec(dllimport)
-# else
-#  define EVENT2_EXPORT_SYMBOL
-# endif
+# define EVENT2_EXPORT_SYMBOL
 
 #endif /* event_*_EXPORTS */
 
-#if defined(_MSC_VER)
-# define EVENT2_EXPORT_SYMBOL_DECL __declspec(dllimport)
-#else
-# define EVENT2_EXPORT_SYMBOL_DECL extern
-#endif
-
 #endif /* EVENT2_VISIBILITY_H_INCLUDED_ */

log-internal.h

@@ -48,8 +48,7 @@ extern "C" {
 #endif
 
 #ifdef EVENT_DEBUG_LOGGING_ENABLED
-EVENT2_EXPORT_SYMBOL_DECL
-ev_uint32_t event_debug_logging_mask_;
+EVENT2_EXPORT_SYMBOL extern ev_uint32_t event_debug_logging_mask_;
 #define event_debug_get_logging_mask_() (event_debug_logging_mask_)
 #else
 #define event_debug_get_logging_mask_() (0)

log.c

@@ -69,8 +69,7 @@ static event_fatal_cb fatal_fn = NULL;
 #define DEFAULT_MASK 0
 #endif
 
-EVENT2_EXPORT_SYMBOL
-ev_uint32_t event_debug_logging_mask_ = DEFAULT_MASK;
+EVENT2_EXPORT_SYMBOL ev_uint32_t event_debug_logging_mask_ = DEFAULT_MASK;
 #endif /* EVENT_DEBUG_LOGGING_ENABLED */
 
 void