fix memory leak in expand_mmac_params

When running with -fsanitize=leak enabled nasm prints this error:

Direct leak of 10 byte(s) in 5 object(s) allocated from:
    #0 0x7f52b6464867 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145
    netwide-assembler#1 0x55cf36676bc4 in nasm_malloc nasmlib/alloc.c:55
    netwide-assembler#2 0x55cf3667730d in nasm_vaxprintf nasmlib/asprintf.c:61
    netwide-assembler#3 0x55cf36677618 in nasm_asprintf nasmlib/asprintf.c:90
    netwide-assembler#4 0x55cf366e8b96 in expand_mmac_params asm/preproc.c:5451
    netwide-assembler#5 0x55cf366fec7a in pp_tokline asm/preproc.c:7767
    netwide-assembler#6 0x55cf366ff84a in pp_getline asm/preproc.c:7837
    netwide-assembler#7 0x55cf3667263c in assemble_file asm/nasm.c:1722
    netwide-assembler#8 0x55cf3666b4e4 in main asm/nasm.c:719
    netwide-assembler#9 0x7f52b5b7cd8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
    netwide-assembler#10 0x7f52b5b7ce3f in __libc_start_main_impl ../csu/libc-start.c:392
    netwide-assembler#11 0x55cf36666e04 in _start (/home/ivan/d/nasm/nasm+0x2e2e04)

This error is reproducing on lnxhello.asm test.

Signed-off-by: Ivan Sorokin <vanyacpp@gmail.com>

Author: sorokin

asm/preproc.c

@@ -5555,7 +5555,7 @@ static Token *expand_mmac_params(Token * tline)
             } else {
                 *tail = t;
                 tail = &t->next;
-		set_text(t, text, tok_strlen(text));
+                set_text_free(t, text, tok_strlen(text));
                 t->type = type;
             }
             changed = true;