dbghelp: Mimic native behavior for module name.

dbghelp: Mimic native behavior for module name.

Module names appear in three spots in dbghelp:
  A) SymGetModuleInfo() .ModuleName
  B) module enumeration (as parameter in callback)
  C) in symbol/type research in module!name form

Tests show that:
- A) and B) always use only the derivation of the image
  name, whatever the passed module name in SymLoadModule().
- C) can use either the form derived from image name
  {as A) and B)}, but also the passed module name in
  SymLoadModule().

Note: B) is limited to 64 characters, while A) is limited to 32
characters (not tested here).

Signed-off-by: Eric Pouech <epouech@codeweavers.com>