Modified the default HTTP headers used by libcurl:

A) Normal non-proxy HTTP:

 - no more "Pragma: no-cache" (this only makes sense to proxies)

B) Non-CONNECT HTTP request over proxy:

 - "Pragma: no-cache" is used (like before)
 - "Proxy-Connection: Keep-alive" (for older style 1.0-proxies)

C) CONNECT HTTP request over proxy:

 - "Host: [name]:[port]"
 - "Proxy-Connection: Keep-alive"

tests/data/test234

@@ -70,6 +70,7 @@ Authorization: Basic aWFtOm15c2VsZg==
 Host: first.host.it.is
 Pragma: no-cache
 Accept: */*
+Proxy-Connection: Keep-Alive
 
 GET http://goto.second.host.now/2340002 HTTP/1.1
 Proxy-Authorization: Basic dGVzdGluZzp0aGlz
@@ -77,6 +78,7 @@ Authorization: Basic aWFtOm15c2VsZg==
 Host: goto.second.host.now
 Pragma: no-cache
 Accept: */*
+Proxy-Connection: Keep-Alive
 
 </protocol>
 </verify>