compiler warning fixes

The fix for tools/convert-trace/Gem5Converter.cc repairs a real issue
which caused a runtime warning to never be displayed.

Change-Id: I5d94acdbffc99d5f2a78f047062c011c6f8ab4e3

src/core/sal/bochs/CompressState.ah

@@ -74,7 +74,7 @@ aspect CompressState {
 		} while (remaining);
 		gzclose(f);
 
-		return (cbuf - (char *)ptr) / size;
+		return (cbuf - (const char *)ptr) / size;
 	}
 };