Add extern declarations to headers for all global variables

include/d/d_meter.h

@@ -579,6 +579,10 @@ public:
     /* 0x3027 */ u8 field_0x3027;
 };
 
+extern dMeter_map_HIO_c g_meter_mapHIO;
+extern dMeter_HIO_c g_meterHIO;
 extern dMeter_menuHIO_c g_menuHIO;
+extern dMeter_msg_HIO_c g_msgHIO;
+extern dMeter_message_HIO_c g_messageHIO;
 
 #endif /* D_METER_H */

include/d/d_metronome.h

@@ -67,4 +67,6 @@ public:
     /* 0xE3B */ u8 mbOpen;
 };
 
+extern dMn_HIO_c g_mnHIO;
+
 #endif /* D_METRONOME_H */

include/d/d_s_name.h

@@ -175,4 +175,6 @@ public:
     /* 0x1BBC */ int field_0x1bbc;
 };
 
+extern dSn_HIO_c g_snHIO;
+
 #endif /* D_S_NAME */

include/d/d_s_play.h

@@ -117,8 +117,6 @@ public:
     /* 0x10 */ u32 field_0x10;
 };
 
-extern dScnPly_msg_HIO_c g_msgDHIO;
-
 class dScnPly_preLoad_HIO_c : public mDoHIO_entry_c {
 public:
     virtual ~dScnPly_preLoad_HIO_c() {}
@@ -141,8 +139,10 @@ public:
     /* 0x8 */ dScnPly_reg_childHIO_c mChild[22];
 };
 
+extern dScnPly_dark_HIO_c g_darkHIO;
 extern dScnPly_reg_HIO_c g_regHIO;
 extern dScnPly_env_HIO_c g_envHIO;
+extern dScnPly_msg_HIO_c g_msgDHIO;
 
 // Based on Twilight Princess debug, each g_envHIO child here was likely named after a specific developer.
 // However, the developer name for each child isn't known here, so the below macro names are all unofficial.