NTLM_WB: final congruency naming adjustments

Configure script option --enable-wb-ntlm-auth renamed to --enable-ntlm-wb
Configure script option --disable-wb-ntlm-auth renamed to --disable-ntlm-wb

Preprocessor symbol WINBIND_NTLM_AUTH_ENABLED renamed to NTLM_WB_ENABLED
Preprocessor symbol WINBIND_NTLM_AUTH_FILE renamed to NTLM_WB_FILE

Test harness env var CURL_NTLM_AUTH renamed to CURL_NTLM_WB_FILE

Static function wb_ntlm_close renamed to ntlm_wb_cleanup
Static function wb_ntlm_initiate renamed to ntlm_wb_init
Static function wb_ntlm_response renamed to ntlm_wb_response