'Fill area under curve' puts fill above curve if the y axis is logarithmic

[mantid-builder]

Original Reporter: Russell Taylor

This bug existed in Qtiplot as well and was fixed under this ticket and changeset 2319:

http://developer.berlios.de/bugs/?func=detailbug&bug_id=18440&group_id=6626

http://svn.berlios.de/viewvc/qtiplot?view=revision&revision=2319

[mantid-builder]

This issue was originally trac ticket 5025