[REVIEW][3-5] fdo#48647 ugly hairline double border drawing regression

[Michael Stahl]

hi all,

today's border line regression fix is for fdo#48647, which is simply
missing usage of the ClipRegion to clip the hairline border lines, fix
proposed for libreoffice-3-5:

http://cgit.freedesktop.org/libreoffice/core/commit/?id=49bd0e4e6bb0ed0671de72d84700ddcc49828f69

please note that because commit
2c91cb08d65cd35fa8ef6eaca3677aa82fb58cbe
changed the hairline predicates on master such that a
border in Writer is never considered a hairline
(because Writer borders are never thinner than 1 twip),
this bug cannot actually be observed in Writer on master now,
but it can be observed in Calc on master.