Bug 446454 - [GTK+] Make GTK+ 2.18 the minimum supported version

Change-Id: I622c5f3a024f9937f103e45736f863c60a7439f4
Signed-off-by: Arun Thondapu <arunkumar.thondapu@in.ibm.com>
Bug 446534 - [10.10] Table/tree with column headers visible has issues
on OS X 10.10 Yosemite