[sigc] recent sigc++ and Objective C/Cocoa/Carbon

[Paul Davis <paul linuxaudiosystems com>]

looks like one or more of Objective C/Cocoa/Carbon has taken the
hairbrained step of #define-ing "nil". this makes this construction:

   struct nil ....

in functors/functor_trait.h a little dubious.

in fact, all these headers on OS X 10.4 include "#define nil" ...

/Developer/SDKs/MacOSX10.3.9.sdk/Developer/Headers/CFMCarbon/CarbonCore/MacTypes.h
/Developer/SDKs/MacOSX10.3.9.sdk/Developer/Headers/CFMCarbon/MacTypes.h
/Developer/SDKs/MacOSX10.3.9.sdk/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/CarbonCore.framework/Versions/A/Headers/MacTypes.h
/Developer/SDKs/MacOSX10.3.9.sdk/System/Library/Frameworks/Foundation.framework/Versions/C/Headers/NSObjCRuntime.h
/Developer/SDKs/MacOSX10.3.9.sdk/usr/include/objc/objc.h
/Developer/SDKs/MacOSX10.4u.sdk/Developer/Headers/CFMCarbon/CarbonCore/MacTypes.h
/Developer/SDKs/MacOSX10.4u.sdk/Developer/Headers/CFMCarbon/MacTypes.h
/Developer/SDKs/MacOSX10.4u.sdk/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/CarbonCore.framework/Versions/A/Headers/MacTypes.h
/Developer/SDKs/MacOSX10.4u.sdk/System/Library/Frameworks/Foundation.framework/Versions/C/Headers/NSObjCRuntime.h
/Developer/SDKs/MacOSX10.4u.sdk/usr/include/objc/objc.h
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/CarbonCore.framework/Versions/A/Headers/MacTypes.h
/System/Library/Frameworks/Foundation.framework/Versions/C/Headers/NSObjCRuntime.h

clearly, ObjC/Cocoa/Carbon are in the wrong, but would it be wise to
protect sigc++ from this stupidity?

--p