Added env_get_environ_p() as more portable way of accessing environ variable. Implemented with OS X using _NSGetEnviron().

Added env_clean_except()

lib_deinit() now frees memory used by env_put(). --HG-- branch : HEAD

Added env_backup_*() for saving/restoring environment. --HG-- branch : HEAD

Added env_remove(). --HG-- branch : HEAD

Reverted "environment array" changes. It broke overriding imap/pop3 settings from userdb and the performance improvements weren't all that great anyway. --HG-- branch : HEAD

Added functions for building an "environment array". It can be passed later to execve(). --HG-- branch : HEAD

Changed .h ifdef/defines to use <NAME>_H format. --HG-- branch : HEAD

Removed restrict_access_clean_env() and env_remove(). They're not needed. --HG-- branch : HEAD

Added env_remove() and restrict_access_clear_env(). --HG-- branch : HEAD

Created env_put() and env_clean() for a bit easier handling of environment variables. --HG-- branch : HEAD