[libsigc++2] Remove the (generated) sigc++/object_slot.h header.

[Murray Cumming <murrayc src gnome org>]

commit 88e88c8d6803a07dccbe2a603926f462520ff974
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Aug 12 10:08:59 2015 +0200

    Remove the (generated) sigc++/object_slot.h header.
    
    Because it now contains no API.
    See https://bugzilla.gnome.org/show_bug.cgi?id=752560#c6

 sigc++/filelist.am             |    4 ++--
 sigc++/macros/object_slot.h.m4 |   22 ----------------------
 2 files changed, 2 insertions(+), 24 deletions(-)
---
diff --git a/sigc++/filelist.am b/sigc++/filelist.am
index 32a4f80..dd09d22 100644
--- a/sigc++/filelist.am
+++ b/sigc++/filelist.am
@@ -17,11 +17,11 @@
 
 # Base (./)
 base_m4 = template.macros.m4 signal.h.m4 slot.h.m4 \
-         object_slot.h.m4 hide.h.m4 retype.h.m4 \
+         hide.h.m4 retype.h.m4 \
          limit_reference.h.m4
 base_built_cc =
 base_built_h = signal.h slot.h \
-              object_slot.h hide.h retype.h limit_reference.h
+              hide.h retype.h limit_reference.h
 
 # Functors (functors/)
 functors_m4 = functor_trait.h.m4 slot.h.m4 ptr_fun.h.m4 mem_fun.h.m4