Build Errors Examples Using LLVM/Clang on Windows

The following two bits of code compile ok with MSVC, but using LLVM/Clang produces the following errors.

Using the code in print.cpp

```
BOOST_HOF_STATIC_FUNCTION(simple_print) = fix(first_of(
BOOST_HOF_LIFT(print_with_cout),
BOOST_HOF_LIFT(print_with_range),
BOOST_HOF_LIFT(print_with_tuple)
));

```
produces the following error

```
1>./boost_hof_functions.h(45): error : templates cannot be declared inside of a local class
1>C:\boost_1_68_0\boost/hof/lift.hpp(90): note: expanded from macro 'BOOST_HOF_LIFT'
1>C:\boost_1_68_0\boost/hof/lift.hpp(105): note: expanded from macro 'BOOST_HOF_LIFT_CLASS'
```

And

`BOOST_HOF_STATIC_LAMBDA_FUNCTION(print) = boost::hof::proj(simple_print);`

produces

```
>./boost_hof_functions.h(51): error : non-const lvalue reference to type 'reveal_adaptor<...>' cannot bind to a temporary of type 'reveal_adaptor<...>'
1>C:\boost_1_68_0\boost/hof/lambda.hpp(241): note: expanded from macro 'BOOST_HOF_STATIC_LAMBDA_FUNCTION']
```

There are nearly identical errors with functions from in.cpp.