To work correctly in a multi-threaded environment, curl needs to be
used with CURLOPT_NOSIGNAL set to 1.  If it's left at zero, the
default, then curl will use signals to deal with timeouts which will
often result in a crash.

ref: http://curl.haxx.se/libcurl/c/libcurl-tutorial.html#Multi-threading
ref: http://curl.haxx.se/libcurl/c/CURLOPT_NOSIGNAL.html
ref: http://stackoverflow.com/questions/9191668/error-longjmp-causes-uninitialized-stack-frame
ref: https://bugzilla.redhat.com/show_bug.cgi?id=539809
ref: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=570436