[inplace_function] make it usable without exceptions

[AndWass]

The throw std::bad_function_call(); in the default constructor of vtable causes compilation failures when building with -fno-exceptions.

What to do instead, I don't really know, but one of the use-cases I have for this is in an embedded setting and this is throwing a wrench in that unfortunately.

[Quuxplusone]

I suggest adding this to the top of the header:

#ifndef SG14_INPLACE_FUNCTION_THROW
#define SG14_INPLACE_FUNCTION_THROW(x) throw (x)
#endif

and then we use SG14_INPLACE_FUNCTION_THROW(std::bad_function_call()); in the vtable.

And if you don't want the throw, you just #define SG14_INPLACE_FUNCTION_THROW(x) __builtin_unreachable() or assert(false) or whatever.

[AndWass]

Yah that sounds like a good solution.