Change c++ standard to c++17

Author: SiskaPavel

configure.ac

@@ -20,7 +20,7 @@ RPM_BUILDREQ=
 
 AC_CONFIG_MACRO_DIR([m4])
 # Must be checked before default -g -O2 is set:
-CXXFLAGS=" -std=gnu++11 "
+CXXFLAGS=" -std=gnu++17 "
 AC_ARG_ENABLE([debug],
         AC_HELP_STRING([--enable-debug],
         [Enable build with debug symbols and without optimizations.]),