Also define function EclipseState::hasInputLgr

Otherwise people will experience linker error when trying to use it.

Closes #3787

src/opm/input/eclipse/EclipseState/EclipseState.cpp

@@ -275,6 +275,10 @@ namespace Opm {
         return !m_inputNnc.input().empty();
     }
 
+    bool EclipseState::hasInputLGR() const {
+        return m_lgrs.size();
+    }
+
     void EclipseState::initLgrs(const Deck& deck) {
         if (!DeckSection::hasGRID(deck))
             return;

tests/parser/LgrTests.cpp

@@ -101,6 +101,7 @@ SCHEDULE
     Opm::EclipseState state(deck);
     Opm::LgrCollection lgrs = state.getLgrs();
 
+    BOOST_CHECK(state.hasInputLGR());
     BOOST_CHECK_EQUAL( lgrs.size() , 2U );
     BOOST_CHECK(lgrs.hasLgr("LGR1"));
     BOOST_CHECK(lgrs.hasLgr("LGR2"));