curl -E: allow to escape ':' in cert nickname
curl.1: document escape sequences recognized by -E
tool_getparam: describe what parse_cert_parameter() does

... and de-duplicate the code initializing *passphrase
tool_getparam: fix memleak in handling the -E option
tool_getparam: ensure string termination in parse_cert_parameter()
src/Makefile.am: build static lib for unit tests if enabled
unit1394.c: basis of a unit test for parse_cert_parameter()
unit1394.c: plug the curl tool unit test in