Update acces to netstats for 2.6.29

Update acces to netstats for 2.6.29
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The successor of dev->get_stats(dev) in 2.6.29 is dev_get_stats(dev)
which provides a const(!) pointer for read only access to the stats.
As the usual current method to access the stats is to reference
dev->stats directly as stats is part of the struce netdevice
since 2.6.23 this patch implements this method of access now.
For kernels < 2.6.23 the netstats are part of the private data
and only this is handled by a separate wrapper now.
The idea was also to get a proper source code after strip-src.

git-svn-id: svn://svn.berlios.de//socketcan/trunk@901 030b6a49-0b11-0410-94ab-b0dab22257f2