fixed compiler detection -> removes a lot of warnings

include/ACGL/ACGL.hh

@@ -39,6 +39,18 @@
  *
  */
 
+// defines a one-macro version number for easy compare functions: e.g. gcc 4.6.2 -> 406020
+// see http://sourceforge.net/apps/mediawiki/predef/index.php?title=Compilers for macros to detect compilers
+#if defined(__GNUC__)
+# if defined(__GNUC_PATCHLEVEL__)
+#  define __GNUC_VERSION__ (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
+# else
+#  define __GNUC_VERSION__ (__GNUC__ * 10000 + __GNUC_MINOR__ * 100)
+# endif
+#else
+#  define __GNUC_VERSION__ 0
+#endif
+
 #if ((__cplusplus >= 201103L) || (__STDC_VERSION__ >= 201112L) || defined(__GXX_EXPERIMENTAL_CXX0X__))
    // last C++11 draft or final C++11 standart or C++11 via -std=c++0x on gcc:
 #  include <memory>