Code now follows these guidelines:
- define PDB & Codeview internals in cvconst.h and mscvinfo.h (instead
  of having definitions in .c files, some of them being duplicate of .h
  content, and their "duplicate" values eventually diverged over time)
- index of first type comes from PDB type header (instead of always being
  hardcoded as FIRST_DEFINABLE_TYPE)
- use index of last typex from type header (instead of guessing the right
  value while parsing types, which also allows a single allocation
  instead of enlarging buffer while parsing).
Signed-off-by: Eric Pouech <eric.pouech@gmail.com>