dconfig: Change export macros to EXP*_DTOOL_DCONFIG

This is for consistency with `panda`, which follows this format.

dtool/src/dconfig/config_dconfig.h

@@ -23,7 +23,7 @@
 #include "dtoolbase.h"
 #include "notifyCategoryProxy.h"
 
-NotifyCategoryDecl(dconfig, EXPCL_DTOOLCONFIG, EXPTP_DTOOLCONFIG);
-NotifyCategoryDecl(microconfig, EXPCL_DTOOLCONFIG, EXPTP_DTOOLCONFIG);
+NotifyCategoryDecl(dconfig, EXPCL_DTOOL_DCONFIG, EXPTP_DTOOL_DCONFIG);
+NotifyCategoryDecl(microconfig, EXPCL_DTOOL_DCONFIG, EXPTP_DTOOL_DCONFIG);
 
 #endif

dtool/src/dconfig/dconfig.h

@@ -30,7 +30,7 @@
  * used primarily by Python code.  For modern code, use the new
  * ConfigVariable* interface instead of this deprecated interface.
  */
-class EXPCL_DTOOLCONFIG DConfig {
+class EXPCL_DTOOL_DCONFIG DConfig {
 PUBLISHED:
   static INLINE bool GetBool(const string &sym, bool def = false);
   static INLINE int GetInt(const string &sym, int def = 0);

dtool/src/dtoolbase/dtoolsymbols.h

@@ -109,6 +109,9 @@
 #define EXPCL_DTOOL_PRC EXPCL_DTOOLCONFIG
 #define EXPTP_DTOOL_PRC EXPTP_DTOOLCONFIG
 
+#define EXPCL_DTOOL_DCONFIG EXPCL_DTOOLCONFIG
+#define EXPTP_DTOOL_DCONFIG EXPTP_DTOOLCONFIG
+
 
 /* These two are always defined empty, because pystub is statically
    built.  But we leave the symbol around in case we change our minds