Werk #7505: Updated rrdtool to version 1.5.4

Component	Other components
Title	Updated rrdtool to version 1.5.4
Date	Aug 26, 2015
Level	Trivial Change
Class	New Feature
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	1.2.7i3 Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk MSP (CME)

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