[MINOR] Capture & display more data from health checks, v2

Capture & display more data from health checks, like
strerror(errno) for L4 failed checks or a first line
from a response for L7 successes/failed checks.

Non ascii or control characters are masked with
chunk_htmlencode() (html stats) or chunk_asciiencode() (logs).
diff --git a/include/common/defaults.h b/include/common/defaults.h
index c09f5a4..b0aee86 100644
--- a/include/common/defaults.h
+++ b/include/common/defaults.h
@@ -174,4 +174,9 @@
 #define MAX_HOSTNAME_LEN	32
 #endif
 
+/* Maximum health check description length */
+#ifndef HCHK_DESC_LEN
+#define HCHK_DESC_LEN	128
+#endif
+
 #endif /* _COMMON_DEFAULTS_H */