Fixed the setting of CVAPI_EXPORTS for modules that are always static/shared.

Also, removed needless check of BUILD_SHARED_LIBS in core; in that case,
only the current module's library type matters.

cmake/OpenCVModule.cmake

@@ -508,7 +508,8 @@ macro(ocv_create_module)
     )
   endif()
 
-  if(BUILD_SHARED_LIBS)
+  if((NOT DEFINED OPENCV_MODULE_TYPE AND BUILD_SHARED_LIBS)
+      OR (DEFINED OPENCV_MODULE_TYPE AND OPENCV_MODULE_TYPE STREQUAL SHARED))
     if(MSVC)
       set_target_properties(${the_module} PROPERTIES DEFINE_SYMBOL CVAPI_EXPORTS)
     else()

modules/core/src/system.cpp

@@ -779,7 +779,7 @@ cvGetModuleInfo( const char* name, const char **version, const char **plugin_lis
         *plugin_list = plugin_list_buf;
 }
 
-#if defined BUILD_SHARED_LIBS && defined CVAPI_EXPORTS && defined WIN32 && !defined WINCE
+#if defined CVAPI_EXPORTS && defined WIN32 && !defined WINCE
 BOOL WINAPI DllMain( HINSTANCE, DWORD  fdwReason, LPVOID );
 
 BOOL WINAPI DllMain( HINSTANCE, DWORD  fdwReason, LPVOID )