opts: document CURLE_OUT_OF_MEMORY as RETURN VALUE

docs/libcurl/opts/CURLOPT_CAINFO.3

docs/libcurl/opts/CURLOPT_COOKIE.3

docs/libcurl/opts/CURLOPT_COOKIEJAR.3

docs/libcurl/opts/CURLOPT_CUSTOMREQUEST.3

docs/libcurl/opts/CURLOPT_EGDSOCKET.3

docs/libcurl/opts/CURLOPT_FTPPORT.3

docs/libcurl/opts/CURLOPT_INTERFACE.3

docs/libcurl/opts/CURLOPT_KEYPASSWD.3

docs/libcurl/opts/CURLOPT_KRBLEVEL.3

docs/libcurl/opts/CURLOPT_PROXY.3

docs/libcurl/opts/CURLOPT_PROXYUSERPWD.3

docs/libcurl/opts/CURLOPT_RANDOM_FILE.3

docs/libcurl/opts/CURLOPT_RANGE.3

docs/libcurl/opts/CURLOPT_REFERER.3

docs/libcurl/opts/CURLOPT_SSLCERT.3

docs/libcurl/opts/CURLOPT_SSLCERTTYPE.3

docs/libcurl/opts/CURLOPT_SSLENGINE.3

docs/libcurl/opts/CURLOPT_SSLENGINE_DEFAULT.3

docs/libcurl/opts/CURLOPT_SSLKEY.3

docs/libcurl/opts/CURLOPT_SSLKEYTYPE.3