BUG/MINOR: htx: make sure to always initialize the HTTP method when parsing a buffer

smp_prefetch_htx() is used when trying to access the contents of an HTTP
buffer from the TCP rulesets. The method was not properly set in this
case, which will cause the sample fetch methods relying on the method
to randomly fail in this case.

Thanks to Tim Düsterhus for reporting this issue (#97).

This fix must be backported to 1.9.
diff --git a/src/http_fetch.c b/src/http_fetch.c
index 3e6f4d1..2d3a381 100644
--- a/src/http_fetch.c
+++ b/src/http_fetch.c
@@ -270,6 +270,7 @@
 		sl = htx_add_stline(htx, HTX_BLK_REQ_SL, flags, h1sl.rq.m, h1sl.rq.u, h1sl.rq.v);
 		if (!sl || !htx_add_all_headers(htx, hdrs))
 			return NULL;
+		sl->info.req.meth = h1sl.rq.meth;
 	}
 
 	/* OK we just got a valid HTTP message. If not already done by