Use pkg-config to obtain xtables.h path

On openSUSE 12.2 (at least) xtables.h is not installed in the system-wide
include dir but in /usr/include/iptables-1.4.16.3/. This results in the
following build failure:
em_ipset.c:26:21: fatal error: xtables.h: No such file or directory

Other includers of xtables.h already call out to pkg-config
iproute2: clarification of various man8 pages

Rephrasing for clarity.

Note that in ip-rule.8 I rephrased a sentence to "The RPDB is scanned
in order of decreasing priority." The original version talked about
*in*creasing priority, but from the context that didn't make sense.

Signed-off-by: Kees van Reeuwijk <reeuwijk@few.vu.nl>
iproute2: clarifications in the tc-hfsc.7 man page

Improved man page as follows:
- Use more `mainstream' english
- Rephrased for clarity
- Use standard notation for units

Signed-off-by: Kees van Reeuwijk <reeuwijk@few.vu.nl>
iproute2: add a missing return statement

Since do_help() has to return an int to fit in the table of commands,
it should actually return an int. This patch lets it do so.

Signed-off-by: Kees van Reeuwijk <reeuwijk@few.vu.nl>
iproute2: clarifications in the libnetlink.3 man page

Rephrasing for clarity.

Signed-off-by: Kees van Reeuwijk <reeuwijk@few.vu.nl>

 ---

 libnetlink.3 |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)
iproute2: improved error messages

This patch improves many error messages as follows:
- For incorrect parameters, show the value of the offending parameter, rather than just say that it is incorrect
- Rephrased messages for clarity
- Rephrased to more `mainstream' english

Signed-off-by: Kees van Reeuwijk <reeuwijk@few.vu.nl>
ip: make local functions static
lib: make string arguments const

For lookup routines, make arguments const where possible.
Makefile: turn on warnings about missing prototypes

Catches missing, dead code and also places where function should be static.
ip: handle flush with table > 2^31

Fixes Debian bug #700434
Need to table id in filter to be unsigned to avoid conversion to -1

The documentation for "ip" suggests that, when using multiple routing tables, the table ID can be an arbitrary 32 bit number. I've been writing a script that calculates a table Id based on an IP addresses and sets up tables accordingly based on it. This seems to work for everything I've tried except "ip route flush". If you specify a table to flush with an ID over 2^31, it flushes all IPv4 routing tables. For example:

Will delete all routing tables, including the default one. Needless to say, this is quite annoying. I think this is an upstream bug, but your opinions will be greatly appreciated.