Move ANSI C standard prototypes to stdlib.h; leave the gPXE-specific

function prototypes (e.g. malloc_dma()) in malloc.h.

src/include/stdlib.h

@@ -2,5 +2,25 @@
 #define STDLIB_H
 
 extern unsigned long strtoul ( const char *p, char **endp, int base );
+extern void * realloc ( void *old_ptr, size_t new_size );
+extern void * malloc ( size_t size );
+extern void free ( void *ptr );
+
+/**
+ * Allocate cleared memory
+ *
+ * @v nmemb		Number of members
+ * @v size		Size of each member
+ * @ret ptr		Allocated memory
+ *
+ * Allocate memory as per malloc(), and zero it.
+ *
+ * Note that malloc() and calloc() are identical, in the interests of
+ * reducing code size.  Callers should not, however, rely on malloc()
+ * clearing memory, since this behaviour may change in future.
+ */
+static inline void * calloc ( size_t nmemb, size_t size ) {
+	return malloc ( nmemb * size );
+}
 
 #endif /* STDLIB_H */