fix compiler warning

convert Curl_ultous() and Curl_ultouc() functions to curlx_ultous() and
curlx_ultouc(), exposing them through curlx.h to allow proper code reuse
later in our test harness.

fix compiler warning

fix compiler warning

removed trailing whitespace

in a slightly better way for more platforms. The $HOME is only used for
.curlrc atm, but the possible upcoming change of .netrc treatment may also
need the home dir.