Bug 502301 - Fix binhex_decode array signedness which broke builds on architectures where char is unsigned [r=benjamin]

This was detected by the C++0x narrowing conversion inside {} compilation errors.

netwerk/streamconv/converters/nsBinHexDecoder.cpp

@@ -98,7 +98,7 @@ NS_INTERFACE_MAP_END
 
 // The binhex 4.0 decoder table....
 
-static char binhex_decode[256] =
+static signed char binhex_decode[256] =
 {
   -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
   -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,