Packages with capital names do not get ignored when checked out

[mauritsvanrees]

See plone/buildout.coredev#931. There I needed to do a manual fix because Plone and Products.CMFPlone were checked out, but still pinned in the constraints.

[jensens]

@mauritsvanrees fixed and released

[petschki]

@mauritsvanrees there's one more fix for capital names here #48