Add new stager stager_reverse_http_proxy_pstore

This stager looks for proxy credentials in windows protected storage. If it finds proxy credentials, it will use them to connect back. If it does not find credentials, it will do the same as stager_reverse_http.

Works on:

- Windows Server 2003

- Windows XP

- Internet Explorer versions 4 to 6
Clean the code

Remove debugging functions from block_get_pstore_proxy_auth.asm.
Reduce allocation size to 1kB.
Correct file information
Fix bug on Windows XP

Correct the addresses of functions in pstorec.dll.

Successfully tested on Server 2003 and XP.