mems & leaks

- define_start: set above preprocess_start because now
  preprocess_start is defining macros.

- free "cmd_include_files"
- free defines always (after error-longjmps)
- close all files (after error-longjmps)
- tccpe.c: free imports always
- libtcc.c: call tcc_memstats only after all states have
  been deleted.

tccasm.c

@@ -999,14 +999,13 @@ ST_FUNC int tcc_assemble(TCCState *s1, int do_preprocess)
     Sym *define_start;
     int ret;
 
+    define_start = define_stack;
     preprocess_start(s1);
 
     /* default section is text */
     cur_text_section = text_section;
     ind = cur_text_section->data_offset;
 
-    define_start = define_stack;
-
     /* an elf symbol of type STT_FILE must be put so that STB_LOCAL
        symbols can be safely used */
     put_elf_sym(symtab_section, 0, 0,