[libsigc++2] docs: Refer to it as libsigc++, not libsigc++2.

[Murray Cumming <murrayc src gnome org>]

commit 33410fa76271f5505ab81a11dd25e045d95983e7
Author: Murray Cumming <murrayc murrayc com>
Date:   Sun Mar 6 11:37:15 2016 +0100

    docs: Refer to it as libsigc++, not libsigc++2.

 sigc++/functors/slot_base.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/sigc++/functors/slot_base.h b/sigc++/functors/slot_base.h
index 49f18da..d969751 100644
--- a/sigc++/functors/slot_base.h
+++ b/sigc++/functors/slot_base.h
@@ -34,7 +34,7 @@ typedef void* (*hook)(void*);
  * Derivations of this class can be considered as a link
  * between a slot and the functor that the slot should
  * execute in operator(). This link is needed because in
- * libsigc++2 the slot doesn't necessarily have exactly the
+ * libsigc++ the slot doesn't necessarily have exactly the
  * same function signature as the functor, thus allowing for
  * implicit conversions.
  *