Because NDB_CXXFLAGS is just used in ndb engine, moved NDB_CXXFLAGS from ha_ndbcluster.m4 to ndb/config/common.mk.am.


config/ac-macros/ha_ndbcluster.m4:
  removed NDB_CXXFLAGS.
storage/ndb/config/common.mk.am:
  Added NDB_CXXFLAGS to AM_CXXFLAGS.