* FTSEurofirst 300 up 0.1 pct, Euro STOXX 50 down 0.2 pct
* Euro STOXX 50 hits support on 50-day moving average
* Buying convertibles seen good way to avoid pull-backs
* Barclays halts sell-off sparked by U.S. dark pool lawsuit
* Reuters poll shows further equity gains expected in H2
By Blaise Robinson
PARIS, June 27 (Reuters) - European stocks ended slightly
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