Fl_cocoa.mm:4080:5: error: unknown type name 'NSOperatingSystemVersion'
    NSOperatingSystemVersion version = [[NSProcessInfo processInfo] operatingSystemVersion];
    ^
Fl_cocoa.mm:4080:69: warning: instance method '-operatingSystemVersion' not found (return type defaults to 'id') [-Wobjc-method-access]
    NSOperatingSystemVersion version = [[NSProcessInfo processInfo] operatingSystemVersion];
                                                                    ^~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSProcessInfo.h:20:12: note:
      receiver is instance of class declared here
@interface NSProcessInfo : NSObject {