fix compilation under NET_2_0

(cherry picked from commit 67d6dcdc546c425347394853dba25e5b8ec035dc)
ifdef 4.0 using

(cherry picked from commit f75a9a9520cddd3c5e1997e0945452ee7452e405)
Fix compilation failure of FlowPanelTests
Add missing assembly references to test targets

(partial cherry-pick from 9a8e03aca05275d607cc3e95c7d767e0cb7cc65b)

Change-Id: I31a26013407ee127cf01d3312491e3722892fb9a
Ignore some corlib tests which fail on linux

(cherry picked from commit bb218f4cdeeadded5c6e1a0b4d8c46aff495db53)