remove memleaks using linked allocator

include/mruby.h

@@ -106,8 +106,8 @@ typedef struct mrb_state {
   struct RClass *false_class;
   struct RClass *nil_class;
   struct RClass *symbol_class;
-
   struct RClass *kernel_module;
+
   struct heap_page *heaps;
   struct heap_page *sweeps;
   struct heap_page *free_heaps;
@@ -124,10 +124,10 @@ typedef struct mrb_state {
   int gc_interval_ratio;
   int gc_step_ratio;
   int gc_disabled;
+  struct alloca_header *mems;
 
   mrb_sym symidx;
   struct kh_n2s *name2sym;      /* symbol table */
-  struct kh_s2n *sym2name;      /* reverse symbol table */
 #ifdef INCLUDE_REGEXP
   struct RNode *local_svar;/* regexp */
 #endif
@@ -362,6 +362,7 @@ void mrb_pool_close(struct mrb_pool*);
 void* mrb_pool_alloc(struct mrb_pool*, size_t);
 void* mrb_pool_realloc(struct mrb_pool*, void*, size_t oldlen, size_t newlen);
 int mrb_pool_can_realloc(struct mrb_pool*, void*, size_t);
+void* mrb_alloca(mrb_state *mrb, size_t);
 
 #if defined(__cplusplus)
 }  /* extern "C" { */