Important bug fix for MacOS

Unlike Linux, RTTI does not work in MacOS/clang when the classes
originate from different compile units. I think that Linux's C++
runtime not only checks for identical vtable, but alternatively
for same name. On MacOS, dynamic_cast will fail instead. This fix
solves this issue by placing the important steam format option
specializations into a single specific shared object (the DB plugin).

src/plugins/streamers/cif/db_plugin/dbCIFFormat.h

@@ -25,6 +25,7 @@
 
 #include "dbSaveLayoutOptions.h"
 #include "dbLoadLayoutOptions.h"
+#include "dbPluginCommon.h"
 
 namespace db
 {
@@ -34,7 +35,7 @@ namespace db
  *  NOTE: this structure is non-public linkage by intention. This way it's instantiated
  *  in all compile units and the shared object does not need to be linked.
  */
-class CIFReaderOptions
+class DB_PLUGIN_PUBLIC CIFReaderOptions
   : public FormatSpecificReaderOptions
 {
 public:
@@ -118,7 +119,7 @@ public:
  *  NOTE: this structure is non-public linkage by intention. This way it's instantiated
  *  in all compile units and the shared object does not need to be linked.
  */
-class CIFWriterOptions
+class DB_PLUGIN_PUBLIC CIFWriterOptions
   : public FormatSpecificWriterOptions
 {
 public:

src/plugins/streamers/dxf/db_plugin/dbDXFFormat.h

@@ -25,6 +25,7 @@
 
 #include "dbLoadLayoutOptions.h"
 #include "dbSaveLayoutOptions.h"
+#include "dbPluginCommon.h"
 
 namespace db
 {
@@ -34,7 +35,7 @@ namespace db
  *  NOTE: this structure is non-public linkage by intention. This way it's instantiated
  *  in all compile units and the shared object does not need to be linked.
  */
-class DXFReaderOptions
+class DB_PLUGIN_PUBLIC DXFReaderOptions
   : public FormatSpecificReaderOptions
 {
 public:
@@ -192,7 +193,7 @@ public:
  *  NOTE: this structure is non-public linkage by intention. This way it's instantiated
  *  in all compile units and the shared object does not need to be linked.
  */
-class DXFWriterOptions
+class DB_PLUGIN_PUBLIC DXFWriterOptions
   : public FormatSpecificWriterOptions
 {
 public:

src/plugins/streamers/gds2/db_plugin/dbGDS2Format.h

@@ -25,6 +25,7 @@
 
 #include "dbSaveLayoutOptions.h"
 #include "dbLoadLayoutOptions.h"
+#include "dbPluginCommon.h"
 
 namespace db
 {
@@ -34,7 +35,7 @@ namespace db
  *  NOTE: this structure is non-public linkage by intention. This way it's instantiated
  *  in all compile units and the shared object does not need to be linked.
  */
-class GDS2ReaderOptions
+class DB_PLUGIN_PUBLIC GDS2ReaderOptions
   : public FormatSpecificReaderOptions
 {
 public:
@@ -97,7 +98,7 @@ public:
  *  NOTE: this structure is non-public linkage by intention. This way it's instantiated
  *  in all compile units and the shared object does not need to be linked.
  */
-class GDS2WriterOptions
+class DB_PLUGIN_PUBLIC GDS2WriterOptions
   : public FormatSpecificWriterOptions
 {
 public:

src/plugins/streamers/oasis/db_plugin/dbOASISFormat.h

@@ -25,6 +25,7 @@
 
 #include "dbSaveLayoutOptions.h"
 #include "dbLoadLayoutOptions.h"
+#include "dbPluginCommon.h"
 
 namespace db
 {
@@ -34,7 +35,7 @@ namespace db
  *  NOTE: this structure is non-public linkage by intention. This way it's instantiated
  *  in all compile units and the shared object does not need to be linked.
  */
-class OASISReaderOptions
+class DB_PLUGIN_PUBLIC OASISReaderOptions
   : public FormatSpecificReaderOptions
 {
 public:
@@ -92,7 +93,7 @@ public:
  *  NOTE: this structure is non-public linkage by intention. This way it's instantiated
  *  in all compile units and the shared object does not need to be linked.
  */
-class OASISWriterOptions
+class DB_PLUGIN_PUBLIC OASISWriterOptions
   : public FormatSpecificWriterOptions
 {
 public: