BUG/BUILD: revert accidental change in the makefile from latest SSL fix

Commit 0bed994 ("BUG/MINOR: ssl: correctly initialize ssl ctx for
invalid certificates") accidently left a change in the Makefile
resulting in -ldl being appended to the LDFLAGS. As reported by
Dmitry Sivachenko, this will break build on systems without libdl
such as FreeBSD.

This fix must be backported to 1.5.
(cherry picked from commit cd360cec7ac41aa3c1a7cbaf04559bf4d3666e25)
BUG/MAJOR: buffer: check the space left is enough or not when input data in a buffer is wrapped

HAProxy will crash with the following configuration:

global
    ...
    tune.bufsize 1024
    tune.maxrewrite 0
frontend xxx
    ...
backend  yyy
   ...
   cookie cookie insert maxidle 300s

If client sends a request of which object size is more than tune.bufsize (1024
bytes), HAProxy will crash.

After doing some debugging, the crash was caused by http_header_add_tail2() ->
buffer_insert_line2() while inserting cookie at the end of response header.
Part codes of buffer_insert_line2() are as below:

int buffer_insert_line2(struct buffer *b, char *pos, const char *str, int len)
{
    int delta;

    delta = len + 2;

    if (bi_end(b) + delta >= b->data + b->size)
        return 0;  /* no space left */

    /* first, protect the end of the buffer */
    memmove(pos + delta, pos, bi_end(b) - pos);
    ...
}

Since tune.maxrewrite is 0, HAProxy can receive 1024 bytes once which is equals
to full buffer size.  Under such condition, the buffer is full and bi_end(b)
will be wrapped to the start of buffer which pointed to b->data. As a result,
though there is no space left in buffer, the check condition
	if (bi_end(b) + delta >= b->data + b->size)
will be true, then memmove() is called, and (pos + delta) will exceed the end
of buffer (b->data + b->size), HAProxy crashes

Just take buffer_replace2() as a reference, the other check when input data in
a buffer is wrapped should be also added into buffer_insert_line2().

This fix must be backported to 1.5.

Signed-off-by: Godbach <nylzhaowei@gmail.com>
(cherry picked from commit a6547c1338ab139332a66096d449e7ac1a56a591)
[RELEASE] Released version 1.5.8

Released version 1.5.8 with the following main changes :
    - BUG/MAJOR: buffer: check the space left is enough or not when input data in a buffer is wrapped
    - BUG/BUILD: revert accidental change in the makefile from latest SSL fix