to pe_load_native_module (resp pe_load_builtin_module) to better describe
what those functions actually do.

dbghelp: Cleanups for module loading (lookups on module name and image name are two different things)

- split up module_find_by_name in two different functions:
  + reused module_find_by_name which looks upon the module name
  + added module_is_already_loaded which looks upon the image name
- cleanup module loading using these functions (removed extra parameter
  to pe_load_module_from_pcs)

uses the stored ModuleName (that the dbghelp's caller can override) but rather a
combination of base address and filename for the module.

Most users of bind contexts don't use bound objects or object params, so 
don't create an initial table. Instead, create it on demand and use an 
exponential algorithm for increasing the size of the table when full.

Spotted by Ron Yorston.

Thanks to Dmitry Timoshkov for a test case.