make_map<int>(make_vector()) cannot be compiled

I'm about to make a `boost::fusion::map>>` object, but the following code won't be compiled.
```
#include
#include

int main() {
boost::fusion::make_map(boost::fusion::make_vector());
}
```
You can try it here: https://wandbox.org/permlink/9t5X0yHFBW5eZ2xC

Since `boost::fusion::map` looked to be doing something special if passed data is sequence, I took a look at the document but could find nothing about it. What's wrong?

Start with the minimal reproducer and the included headers, boost/fusion/include/make_map.hpp and boost/fusion/include/make_vector.hpp. Compare the available make_map and make_vector() interfaces to determine whether the call is supported and why compilation fails. Done means documenting the cause or confirming a library bug, with a regression test if a fix is warranted.

Written by the indexing model from the issue text.