#1 fix sigslot.h to compile with GCC 3.X

[Joseph VanAndel]

Bug 737256 states that GCC 3.x produces a large number
of warnings that "implicit typename is deprecated", e.g.:

SigSlot.h:2379: warning: `typename
Gooey::Signal8<Type1, Type2,
Type3, Type4, Type5, Type6, Type7,
Type8>::ConnectionList::const_iterator' is implicitly a
typename
SigSlot.h:2379: warning: implicit typename is
deprecated, please see
the documentation for details.

The solution is to modify the typedef statements that
use templates from:

typedef std::set<_signal_base<mt_policy> *> sender_set;
typedef sender_set::const_iterator const_iterator;

to:
typedef typename std::set<_signal_base<mt_policy> *>
sender_set;
typedef typename sender_set::const_iterator const_iterator;

I've attached a context diff that suppresses all the
warnings.

[Joseph VanAndel]

context diff - suppress GCC 3.X warnings re implicit typenames