Use size_t for lengths in stream objects

Provides safety against them accidentally becoming negative because
of bugs in the calculations.

Also does the same to CharArray and friends as they were strongly
connection to the stream objects.

common/rdr/MemInStream.h

@@ -36,7 +36,7 @@ namespace rdr {
 
   public:
 
-    MemInStream(const void* data, int len, bool deleteWhenDone_=false)
+    MemInStream(const void* data, size_t len, bool deleteWhenDone_=false)
       : start((const U8*)data), deleteWhenDone(deleteWhenDone_)
     {
       ptr = start;
@@ -48,12 +48,12 @@ namespace rdr {
         delete [] start;
     }
 
-    int pos() { return ptr - start; }
-    void reposition(int pos) { ptr = start + pos; }
+    size_t pos() { return ptr - start; }
+    void reposition(size_t pos) { ptr = start + pos; }
 
   private:
 
-    int overrun(int itemSize, int nItems, bool wait) { throw EndOfStream(); }
+    size_t overrun(size_t itemSize, size_t nItems, bool wait) { throw EndOfStream(); }
     const U8* start;
     bool deleteWhenDone;
   };