fix up prototypes to avoid -Wimplicit-function-declaration warnings

--- a/src/coreui.h
+++ b/src/coreui.h
@@ -177,6 +177,7 @@
 void stepIt_setupGtk(CTR cnt);
 
 void runIt_setupX(void);
+void runIt_setupGtk(void);
 
 
 /*--------------------------------------------------------------------------
--- a/src/ssGtk.c
+++ b/src/ssGtk.c
@@ -82,6 +82,7 @@
 
 /* externals */
 extern dataStart;
+ADDR iAinstAddr(ADDR baseAddr, BYTE iAmode, int delta);
 
 static GtkLabel* instcount_label;
 /* sits in a background loop */
@@ -100,7 +101,7 @@
 }
 
 
-void runIt_setupGtk(void *data)
+void runIt_setupGtk(void)
 {
 	g_idle_add(runItGtk, NULL);
 	stopPressed = NO;