Added .gitattributes file

Author: VolkerEnderlein

.gitattributes

@@ -0,0 +1,10 @@
+# Support GitHub linguist library to display right repository language
+*.cxx.in linguist-language=C++
+*.cpp.in linguist-language=C++
+*.h.in linguist-language=C++
+configure linguist-generated
+configure.ac linguist-generated
+Makefile.in linguist-generated
+Makefile.am linguist-generated
+ltmain.sh linguist-generated
+install-sh linguist-generated