There is several bugs in m4/libssh2.m4 file that broke --with-ssh2 configuration process. All the discussion on the forum at http://www.zabbix.com/forum/showthread.php?t=16283 topic and there is fixed m4 file contents:

1. LIBSSH2_CHECK_CONFIG ([DEFAULT-ACTION])
2. ----------------------------------------------------------
3. Alexander Vladishev Oct-26-2009
   #
4. Checks for ssh2. DEFAULT-ACTION is the string yes or no to
5. specify whether to default to --with-ssh2 or --without-ssh2.
6. If not supplied, DEFAULT-ACTION is no.
   #
7. This macro #defines HAVE_SSH2 if a required header files are
8. found, and sets @SSH2_LDFLAGS@, @SSH2_CFLAGS@ and @SSH2_LIBS@
9. to the necessary values.
   #
10. Users may override the detected values by doing something like:
11. SSH2_LIBS="-lssh2" SSH_CFLAGS="-I/usr/myinclude" ./configure
    #
12. This macro is distributed in the hope that it will be useful,
13. but WITHOUT ANY WARRANTY; without even the implied warranty of
14. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

AC_DEFUN([LIBSSH2_TRY_LINK],
[
AC_TRY_LINK(
[
#include <libssh2.h>
],
[
LIBSSH2_SESSION *session;
session = libssh2_session_init();
],
found_ssh2="yes",)
])dnl

AC_DEFUN([LIBSSH2_CHECK_CONFIG],
[
AC_ARG_WITH(ssh2,[
If you want to use SSH2 based checks:
AC_HELP_STRING([--with-ssh2@<:@=DIR@:>@],[use SSH2 package @<:@default=no@:>@, DIR is the SSH2 library install directory.])],
[
if test "$withval" = "no"; then
want_ssh2="no"
_libssh2_dir="no"
elif test "$withval" = "yes"; then
want_ssh2="yes"
_libssh2_dir="no"
else
want_ssh2="yes"
_libssh2_dir=$withval
fi
],[want_ssh2=ifelse([$1],,[no],[$1])]
)

if test "x$want_ssh2" = "xyes"; then
AC_MSG_CHECKING(for SSH2 support)
if test "x$_libssh2_dir" = "xno"; then
if test -f /usr/include/libssh2.h; then
SSH2_CFLAGS=-I$/usr/include
SSH2_LDFLAGS=-L$/usr/lib
SSH2_LIBS="-lssh2"
found_ssh2="yes"
elif test -f /usr/local/include/libssh2.h; then
SSH2_CFLAGS=-I$/usr/local/include
SSH2_LDFLAGS=-L$/usr/local/lib
SSH2_LIBS="-lssh2"
found_ssh2="yes"
else #libraries are not found in default directories
found_ssh2="no"
AC_MSG_RESULT(no)
fi # test -f /usr/include/libssh2.h; then
else # test "x$_libssh2_dir" = "xno"; then
if test -f $_libssh2_dir/include/libssh2.h; then
SSH2_CFLAGS=-I$_libssh2_dir/include
SSH2_LDFLAGS=-L$_libssh2_dir/lib
SSH2_LIBS="-lssh2"
found_ssh2="yes"
else #if test -f $_libssh2_dir/include/libssh2.h; then
found_ssh2="no"
AC_MSG_RESULT(no)
fi #test -f $_libssh2_dir/include/libssh2.h; then
fi #if test "x$_libssh2_dir" = "xno"; then
fi # if test "x$want_ssh2" != "xno"; then

if test "x$found_ssh2" == "xyes"; then
am_save_cflags="$CFLAGS"
am_save_ldflags="$LDFLAGS"
am_save_libs="$LIBS"

CFLAGS="$CFLAGS $SSH2_CFLAGS"
LDFLAGS="$LDFLAGS $SSH2_LDFLAGS"
LIBS="$LIBS $SSH2_LIBS"

found_ssh2="no"
LIBSSH2_TRY_LINK([no])

CFLAGS="$am_save_cflags"
LDFLAGS="$am_save_ldflags"
LIBS="$am_save_libs"

if test "x$found_ssh2" == "xyes"; then
AC_DEFINE([HAVE_SSH2], 1, [Define to 1 if you have the 'libssh2' library (-lssh2)])
AC_MSG_RESULT(yes)
else
AC_MSG_RESULT(no)
SSH2_CFLAGS=""
SSH2_LDFLAGS=""
SSH2_LIBS=""
fi
fi

AC_SUBST(SSH2_CFLAGS)
AC_SUBST(SSH2_LDFLAGS)
AC_SUBST(SSH2_LIBS)

])dnl