ulib Add umallocbig() and ufreebig() for non-fragmented allocations

ulib/umalloc/umalloc.h

@@ -7,5 +7,7 @@
 void *umalloc(size_t size);
 void ufree(void *ptr_);
 void *urealloc(void *ptr, size_t newsize);
+void *umallocbig(size_t size);
+void ufreebig(void *addr);
 
 #endif // ULIB_UMALLOC_UMALLOC_H_