Don't construct the string outside of vector

This code caused the string to be constructed and then moved into the
vector. With this change the string in constructed inside the vector.

Author: Robert Alm Nilsson

src/engine/command.cpp

@@ -2798,7 +2798,7 @@ void explodelist(const char *s, std::vector<std::string> &elems, int limit)
 {
     const char *start, *end;
     while((limit < 0 || elems.size() < limit) && parselist(s, start, end))
-        elems.emplace_back(std::string(start, end-start));
+        elems.emplace_back(start, end - start);
 }
 
 char *indexlist(const char *s, int pos)