Update operators to use results of expressions as the return type.

configure detects the presence of decltype, typeof, __typeof__ or boost
to facilitate this, and falls back on a simple implementation for obvious
numeric types if none of these are present.

The type deduction has to go via classes such as:

	template<class L, class R> struct AddType
	{
		typedef TOON_TYPEOF((L()+R())) type;
	};

Because using constructs such as:

// Addition Vector + Vector
template<int Size, typename P1, typename P2, typename B1, typename B2>
Vector<Size, TOON_TYPEOF(P1()+P2())> operator+(const Vector<Size, P1, B1>& v1, const Vector<Size, P2, B2>& v2)
{
	typedef TOON_TYPEOF(P1()+P2()) restype;
	return Vector<Size,restype>(v1, v2, Operator<Internal::Add<restype> >());
}

causes the following error:

TooN/test/test2.cc:15: sorry, unimplemented: mangling typeof, use decltype instead

or

TooN/test/test2.cc:15: sorry, unimplemented: call_expr cannot be mangled due to a defect in the C++ ABI

or

TooN/test/test2.cc:16: internal compiler error: in write_type, at cp/mangle.c:1649
Please submit a full bug report,
with preprocessed source if appropriate.

Makefile.in

@@ -17,6 +17,9 @@ install:
 internal/make_vector.hh:  make_make_vector.awk
 	awk -f make_make_vector.awk > $@
 
+internal/builtin_typeof.h:make_typeof.awk
+	awk -f make_typeof.awk > $@
+
 clean:
 	rm -rf html
 

TooN.h

@@ -3,6 +3,9 @@
 #define TOON_INCLUDE_TOON_H
 #include <iostream>
 #include <cstdlib>
+#include <TooN/internal/config.hh>
+#include <TooN/internal/typeof.hh>
+
 namespace TooN
 {