[pph] Stream merging information (issue 5090041)

[dnovillo@google.com]

http://codereview.appspot.com/5090041/diff/1/gcc/cp/pph-streamer-in.c
File gcc/cp/pph-streamer-in.c (right):

http://codereview.appspot.com/5090041/diff/1/gcc/cp/pph-streamer-in.c#newcode2146
gcc/cp/pph-streamer-in.c:2146: pph_read_namespace_chain (pph_stream
*stream, tree enclosing_namespace)
  2142 /* Read a chain of tree nodes from input block IB. DATA_IN
contains
  2143    tables and descriptors for the file being read.  */
  2144
  2145 tree
  2146 pph_read_namespace_chain (pph_stream *stream, tree
enclosing_namespace)

ENCLOSING_NAMESPACE needs documenting.  Would it be better to have the
original pph_read_chain() get this argument?  Not crazy about this
duplication of code.

Same comment applies to the other two routines that the patch
duplicates.

http://codereview.appspot.com/5090041/