v1.2.5: BUG/MINOR: fixed program crash in asynchronous mode

If asynchronous exchange of packets between HAProxy and spoa-mirror is
allowed, when sending a reply to HAProxy, the program crashes in the
tcp_send() function (because at that point the frame->client is a NULL
pointer due to asynchronous mode).

Version of the program changed to v1.2.5.

v1.2.4: BUG/MINOR: removed false positive warning when parsing HTTP headers

The error should be printed only in case there really is an error, that is,
http header is not found and we are not at the end of the buffer.

v1.2.1: BUG/MINOR: fixed parsing of HAPROXY-HELLO capabilities

Version of the program changed to v1.2.1.

v1.2.0: MINOR: added support for HTTP/2 protocol

Additionally, a configuration file test/haproxy-htx.cfg was added to
test the work of the program using the HTTP/2 protocol.

Version of the program changed to v1.2.0.

v1.0.1: BUG/MINOR: fixed checking of healthcheck requests

Version of the program changed to v1.0.1.

v1.0.0

MINOR: supported older versions of the cURL library (up from 7.32.0)