In nettle/md5.h, md5_init and md5_update are defined as macros to
nettle_md5_init and nettle_md5_update respectively. This causes
error when using MD5_params.md5_init and md5_update. This patch
renames these members as md5_init_func and md5_update_func to
avoid name conflict. For completeness, MD5_params.md5_final was
also renamed as md5_final_func.
The changes in curl_ntlm_core.c is conversion error and fixed by
casting to proper type.
It is now possible to calculate the md5 sum as the stream of buffers
becomes known where as previously it was only possible to calculate the
md5 sum of a pre-prepared buffer.
