Apply patch for icpc (#78)

icpc in some way utilizes the preprocessor of the associated "developer
tools" used by the compiler. This leads to, in some cases, a
preprocessor claiming support for `__tuple_element_packs`, even though
icpc (as of version 21.1) can't actually parse such code.  Just use the
MPARK_TUPLE_ELEMENT_PACK impl with __icc until icpc supports it.

Fixes #77

Author: sbolding-LANL

include/mpark/config.hpp

@@ -50,7 +50,7 @@
 #define MPARK_BUILTIN_UNREACHABLE
 #endif
 
-#if __has_builtin(__type_pack_element)
+#if __has_builtin(__type_pack_element) && !(defined(__ICC))
 #define MPARK_TYPE_PACK_ELEMENT
 #endif