libtcc: new LIBTCCAPI tcc_set_options(TCCState*, const char*str)

This replaces       -> use instead:
-----------------------------------
- tcc_set_linker    -> tcc_set_options(s, "-Wl,...");
- tcc_set_warning   -> tcc_set_options(s, "-W...");
- tcc_enable_debug  -> tcc_set_options(s, "-g");

parse_args is moved to libtcc.c (now tcc_parse_args).

Also some cleanups:
- reorder TCCState members
- add some comments here and there
- do not use argv's directly, make string copies
- use const char* in tcc_set_linker
- tccpe: use fd instead of fp

tested with -D MEM_DEBUG: 0 bytes left

tccelf.c

@@ -240,7 +240,7 @@ ST_FUNC int add_elf_sym(Section *s, addr_t value, unsigned long size,
             } else if (s == tcc_state->dynsymtab_section) {
                 /* we accept that two DLL define the same symbol */
             } else {
-#if 1
+#if 0
                 printf("new_bind=%x new_shndx=%x new_vis=%x old_bind=%x old_shndx=%x old_vis=%x\n",
                        sym_bind, sh_num, new_vis, esym_bind, esym->st_shndx, esym_vis);
 #endif