optimisation : avoid double reading of a DIE when the DIE will be parsed

optimisation : avoid double reading of a DIE when the DIE will be parsed
by a DIE parser

Instead of pre-reading the DIE, first let the parser(s) possibly
parse the DIE. Read (to skip) the DIE data if no parser has parsed it.
OTherwise, just jump to the end of the DIE as established by the parser
that has read the DIE.

This slightly improves the reading of inlined info.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14049