Add ifndef check in the headers (#17)

Fixes #14, #15, #16

Author: RobLoach

include/chaiscript/extras/math.hpp

@@ -1,3 +1,6 @@
+#ifndef CHAISCRIPT_EXTRAS_MATH_HPP_
+#define CHAISCRIPT_EXTRAS_MATH_HPP_
+
 #include <cmath>
 #include <memory>
 
@@ -807,3 +810,5 @@ namespace chaiscript {
     }
   }
 }
+
+#endif /* CHAISCRIPT_EXTRAS_MATH_HPP_ */

include/chaiscript/extras/string_id.hpp

@@ -1,3 +1,5 @@
+#ifndef CHAISCRIPT_EXTRAS_STRING_ID_HPP_
+#define CHAISCRIPT_EXTRAS_STRING_ID_HPP_
 
 #include <cmath>
 #include <memory>
@@ -65,3 +67,4 @@ namespace chaiscript {
   }
 }
 
+#endif /* CHAISCRIPT_EXTRAS_STRING_ID_HPP_ */

include/chaiscript/extras/string_methods.hpp

@@ -14,6 +14,10 @@
  *
  * chai.add(chaiscript::bootstrap::standard_library::vector_type<std::vector<std::string>>("VectorString"));
  */
+
+#ifndef CHAISCRIPT_EXTRAS_STRING_METHODS_HPP_
+#define CHAISCRIPT_EXTRAS_STRING_METHODS_HPP_
+
 #include <algorithm>
 #include <string>
 #include <vector>
@@ -95,3 +99,5 @@ namespace chaiscript {
     }
   }
 }
+
+#endif /* CHAISCRIPT_EXTRAS_STRING_METHODS_HPP_ */