Server does not compile with an older version of libcurl due to the following errors:
httptest.c: In function 'process_httptest':
httptest.c:438: error: 'CURLOPT_KEYPASSWD' undeclared (first use in this function)
httptest.c:438: error: (Each undeclared identifier is reported only once
httptest.c:438: error: for each function it appears in.)
This is because CURLOPT_KEYPASSWD was previously known under different names: see http://curl.haxx.se/libcurl/c/CURLOPT_KEYPASSWD.html .