Intern string literals

We're keeping them around anyway

src/codegen/ast_interpreter.cpp

@@ -1474,7 +1474,7 @@ Value ASTInterpreter::visit_set(AST_Set* node) {
 Value ASTInterpreter::visit_str(AST_Str* node) {
     Box* o = NULL;
     if (node->str_type == AST_Str::STR) {
-        o = parent_module->getStringConstant(node->str_data);
+        o = parent_module->getStringConstant(node->str_data, true);
     } else if (node->str_type == AST_Str::UNICODE) {
         o = parent_module->getUnicodeConstant(node->str_data);
     } else {

src/codegen/irgen/irgenerator.cpp

@@ -1278,8 +1278,9 @@ private:
 
     CompilerVariable* evalStr(AST_Str* node, const UnwindInfo& unw_info) {
         if (node->str_type == AST_Str::STR) {
-            llvm::Value* rtn = embedRelocatablePtr(
-                irstate->getSourceInfo()->parent_module->getStringConstant(node->str_data), g.llvm_value_type_ptr);
+            llvm::Value* rtn
+                = embedRelocatablePtr(irstate->getSourceInfo()->parent_module->getStringConstant(node->str_data, true),
+                                      g.llvm_value_type_ptr);
 
             return new ConcreteCompilerVariable(STR, rtn, true);
         } else if (node->str_type == AST_Str::UNICODE) {

src/core/types.h

@@ -482,13 +482,8 @@ BoxedString* internStringImmortal(llvm::StringRef s);
 // Callers should use this function if they can accept mortal string objects.
 // FIXME For now it just returns immortal strings, but at least we can use it
 // to start documenting the places that can take mortal strings.
-inline BoxedString* internStringMortal(const char* s) {
-    return internStringImmortal(s);
-}
-
 inline BoxedString* internStringMortal(llvm::StringRef s) {
-    assert(s.data()[s.size()] == '\0');
-    return internStringMortal(s.data());
+    return internStringImmortal(s);
 }
 
 // TODO this is an immortal intern for now