Disable PCRE process searching to avoid linking against libprce, which
would cause the build to fail due to a missing dependency. With the
--without-pcre switch, build fails due to an undefined reference, so do
it via CONFIGURE_VARS instead.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
[disable PCRE process searching]
Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

Update to 5.7.3 by refreshing patches; remove 800-format-security
as upstream integrated.
Add libnl dependency in the package Makefile as net-snmp will check
if libnl is enabled in config_os_libs2.
Remove unneeded PKG_FIXUP build variable.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>