Don't define DMLC_LOG_STACK_TRACE on Solaris (#59)
Don't define DMLC_LOG_STACK_TRACE on Solaris (#59)

DMLC_LOG_STACK_TRACE involves use of non-standard header execinfo.h, which
causes compilation failure on Solaris.
dmlc/xgboost,dmlc/rabit,dmlc/rabit,dmlc/xgboost,dmlc/rabit,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/rabit,dmlc/xgboost