The PDB types can contain several times a type definition with an identical
name. It seems to appear when modifying a type in source (like adding new
fields to a struct):
- as the PDB file (generated from first compilation) is updated (and not
  fully rewritten), the debug information for the old type is not flushed;
  a new record (for the same struct name) is emitted, and inserted
  before the old one in the hash table (bucket list).

Even if dbghelp's hash table is different from PDB's internal one (ie
number of buckets & bucket lists are different), we must maintain the order
of records of identical names (they end up in the same bucket) as a lookup
by name *must* return the first record in PDB's order.
Lookup by name is used:
- when resolving a forward definition (to get the full UDT definition
  including for example a struct/class fields's list)
- when searching by type name from dbghelp APIs, like SymGetTypeFromName()

This patch implements the preservation of that order.
Signed-off-by: Eric Pouech <eric.pouech@gmail.com>