Check for HAVE_UNISTD_H before including unistd.h.
There is no HAVE_SYS_TYPES to check.
Tweak the indentation of a few #include directives.

Factorize a couple of call convention matching regular expressions.

Fix converting the typelib file name to Unicode by using the correct
buffer size.

Don't print 'process has terminated' message when detaching from a
process (or backtracing it).

- implemented correct lookup when SymFindFileInPath is called to find
  a PDB file
- added pdb_fetch_file_info to gather relevant information
- when looking for a PDB file (from a .EXE or a .DLL), now using
  SymFindFileInPath to locate the PDB file with the correct
  information

First, native dbghelp doesn't do it, and it crashed windbg, likely
because we got the undocumented arguments wrong.

- implemented SymInitializeW (and made SymInitialize call it)
- implemented Sym{SG}etSearchPathW (and made Sym{SG}etSearchPath
  call them)
- per process search path is now stored as unicode string