Revert "use empty RCPP_CONSTEXPR if icc w/ C++98"

This reverts commit f17ee6a.

Author: eddelbuettel

ChangeLog

@@ -1,11 +1,6 @@
-2017-02-01  Dirk Eddelbuettel  <edd@debian.org>
-
-        * inst/include/Rcpp/algorithm.h (RCPP_CONSTEXPR): Further refinement for
-        Intel compiler without C++11
-
 2017-01-31  Dirk Eddelbuettel  <edd@debian.org>
 
-        * DESCRIPTION (Date, Version): Roll minor version
+        * DESCRIPTION (Date, Version): Roll minor version 
 
         * inst/include/Rcpp/algorithm.h: Allow algorithm.h to be compiler under
         Intel's compiler, add copyright header and include guard

inst/include/Rcpp/algorithm.h

@@ -24,8 +24,6 @@
 
 #if __cplusplus >= 201103L || __INTEL_CXX11_MODE__ == 1
 #    define RCPP_CONSTEXPR constexpr
-#elif defined(__INTEL_COMPILER) 
-#    define RCPP_CONSTEXPR
 #else
 #    define RCPP_CONSTEXPR const
 #endif