Fix lua version

Makefile

@@ -1,4 +1,4 @@
-LUA_VERSION=5.2
+LUA_VERSION=5.1
 INCLUDES=-I/usr/include/lua${LUA_VERSION}
 CXX=g++
 CFLAGS=-fPIC

qalculator.cpp

@@ -23,10 +23,7 @@ Output_struct qalculate(const char* input, bool exact_mode, bool interval_mode,
     // Check evaluation options
     user_evaluation_options.structuring = (structuring_mode ?
         STRUCTURING_FACTORIZE :
-        STRUCTURING_EXPAND);
-    user_evaluation_options.interval_calculation = (interval_mode ?
-        INTERVAL_CALCULATION_VARIANCE_FORMULA :
-        INTERVAL_CALCULATION_NONE);
+        STRUCTURING_SIMPLIFY);
     user_evaluation_options.approximation = (exact_mode ? 
         APPROXIMATION_EXACT :
         APPROXIMATION_APPROXIMATE);