Set proper c++ standard for landgen

AMDmi3 · AMDmi3 · commit 7ead4fd7acf5 · 2018-06-26T15:42:49.000+03:00
diff --git a/Makefile.am b/Makefile.am
@@ -21,7 +21,7 @@ dist_sounds_DATA = sounds/*
 noinst_PROGRAMS = langen
 langen_SOURCES = langen.cpp 
 # Disable optimization, not needed
-langen_CXXFLAGS = -O0
+langen_CXXFLAGS = -O0 -std=c++11
 
 # Generation of language-data.cpp
 language-data.cpp: langen
