Update README and fix small decoder issue.

README

@@ -3,7 +3,7 @@ upb - a minimalist implementation of protocol buffers.
 
 For API documentation, see the header files.
 
-To build:
+To build (the core library is ANSI C and has no dependencies):
 $ make
 
 Other useful targets:
@@ -11,6 +11,11 @@ $ make test
 $ make benchmark
 $ make lua (requires lua libraries to be installed)
 
+The tests and benchmarks have the following dependencies
+(Ubuntu package names in parentheses):
+- Google's protobuf compiler + libraries (protobuf-compiler, libprotobuf-dev)
+- Lua binary and libraries (lua5.1, liblua5.1-dev)
+
 Issue tracking is on Google Code:
   http://code.google.com/p/upb/issues/list
 

src/upb_decoder.c

@@ -68,6 +68,7 @@ static bool upb_pullbuf(upb_decoder *d) {
   d->ptr = upb_string_getrobuf(d->bufstr);
   d->end = d->buf + upb_string_len(d->bufstr);
   d->jit_end = d->end - 20;
+  upb_string_recycle(&d->tmp);
   upb_string_substr(d->tmp, d->bufstr, 0, 0);
   upb_dstate_setmsgend(d);
   return true;