Consolidate FileExists usage in logic bin (bug 5931, r=asherkin).

core/logic/intercom.h

@@ -251,7 +251,6 @@ struct sm_core_t
 	void			(*Log)(const char*, ...);
 	void			(*LogToFile)(FILE *fp, const char*, ...);
 	void			(*LogToGame)(const char *message);
-	bool			(*FileExists)(const char *path);
 	const char *	(*GetCvarString)(ConVar*);
 	size_t			(*Format)(char*, size_t, const char*, ...);
 	size_t			(*FormatArgs)(char*, size_t, const char*,va_list ap);

core/logic/smn_filesystem.cpp

@@ -322,7 +322,7 @@ static cell_t sm_FileExists(IPluginContext *pContext, const cell_t *params)
 
 	if (params[0] >= 2 && params[2] == 1)
 	{
-		return smcore.FileExists(name) ? 1 : 0;
+		return smcore.filesystem->FileExists(name) ? 1 : 0;
 	}
 
 	char realpath[PLATFORM_MAX_PATH];