Do not require objects in streams to have defaults constructors

[thomasm]

The following code does not compile:

#include <tpie/stream.h>
class A {
 A(int b) : a(b) { }
 int a;
};
int main() {
        tpie::ami::stream<A> t;
}

With the following compilation error:

/tpie/bte/stream_stdio.h: In constructor ‘tpie::bte::stream_stdio<T>::stream_stdio(const std::string&, tpie::bte::stream_type, TPIE_OS_SIZE_T) [with T = A]’:
/tpie/stream.h:356:   instantiated from ‘tpie::ami::stream<T, bte_t>::stream() [with T = A, bte_t = tpie::bte::stream_stdio<A>]’
test.cpp:   instantiated from here
tpie/bte/stream_stdio.h:130: error: no matching function for call to ‘A::A()’
test.cpp: note: candidates are: A::A(int)
test.cpp: note:                 A::A(const A&)

The problem is that the BTE's assume that the class can be default-constructed, which is not the case for A in my example above. It should be possible to remove this assumptions, but I haven't investigated whether or not it's practical.

[thomasm]

Fixed in r1804, all different kinds of BTEs can now be created on classes without default constructors.