Improve some rrdupdate error messages

[human]

I've written a tool which uses rrdtool, and it uses stdout to send updates to an rrdupdate process which is started once per "go".

Sometimes I get "illegal attempt to update using time..." error messages. However, that message doesn't say which rrd archive this applies to, and because of the buffering of stdio, the message may appear long after the offending update has been written.

Therefore, it would be beneficial if rrdupdate included the file name of the impacted RRD database in the error messages. I'll attach below two diffs, one to 1.2.27, one to 1.3.0, where the latter is a bit clunky due to restructuring done between the two versions.

[human]

Patch against 1.2.27

[human]

Updated patch for rrdtool 1.3.0

[human]

Updated the patch to 1.3.0 to not have a huge array on the stack but instead use strdup(), so that it's a little less clunky...

[oetiker]

thanks, applied in r1441 anf r1442