Cpp: Add feature enum for new identify

* lang/cpp/src/context.cpp (supported_features2): Add
BinaryAndFineGrainedIdentify
* lang/cpp/src/global.h (Feature2): ditto.

--
This is mostly for compatible code with KF5::Gpgmepp where there
is no hard requirement against gpgme 1.7. With 1.7 a version
check would also suffice.

lang/cpp/src/context.cpp

@@ -1519,6 +1519,7 @@ static const unsigned long supported_features = 0
         ;
 
 static const unsigned long supported_features2 = 0
+        | GpgME::BinaryAndFineGrainedIdentify
         ;
 
 bool GpgME::hasFeature(unsigned long features)

lang/cpp/src/global.h

@@ -131,8 +131,10 @@ enum Feature {
     FeatureMaxValue                            = 0x80000000
 };
 enum Feature2 {
+    BinaryAndFineGrainedIdentify               = 0x00000001, // gpgme >= 1.7.0
     Feature2MaxValue                           = 0x80000000
 };
+
 // use hasFeature( unsigned long, unsigned long ) instead
 GPGMEPP_DEPRECATED_EXPORT bool hasFeature(unsigned long feature);
 GPGMEPP_EXPORT bool hasFeature(unsigned long feature, unsigned long feature2);