Description:
------------
mb_detect_encoding issues warning "Illegal argument", then things go bezerk. Maybe some heap corruption.

Reproduce code:
---------------
<?php
  $str = "\357\277\357\277\275\357\277\275\357\277\275\357\277\275";
  $charset = mb_detect_encoding($str , "WINDOWS-1255,ASCII");
  echo "detect $charset\n";
  $str = mb_convert_encoding($str, "UTF-8", $charset);
  echo "convert %str\n";


Expected result:
----------------
detect WINDOWS-1255
convert <some UTF8-text>

Actual result:
--------------
Warning: mb_detect_encoding(): Illegal argument in ...
detect detec    *** note the corrupted string
Segmentation fault

#0  _zend_mm_alloc_int (heap=0xbbf2b0, size=6) at /home/me/src/php-5.2.8/Zend/zend_alloc.c:1780
#1  0x000000000063f3e0 in _estrndup (s=0xd37e38 "UTF-8", length=6)
    at /home/me/src/php-5.2.8/Zend/zend_alloc.c:2435
#2  0x00000000004ed164 in php_mb_parse_encoding_list (value=0xbbf2b0 "\001", value_length=6, 
    return_list=0x7fffdec7a400, return_size=0x7fffdec7a40c, persistent=0)
    at /home/me/src/php-5.2.8/ext/mbstring/mbstring.c:367
#3  0x00000000004ee602 in php_mb_convert_encoding (input=<value optimized out>, 
    length=<value optimized out>, _to_encoding=<value optimized out>, _from_encodings=0xd37e38 "UTF-8", 
    output_len=0x7fffdec7a468) at /home/me/src/php-5.2.8/ext/mbstring/mbstring.c:2443
#4  0x00000000004eeb44 in zif_mb_convert_encoding (ht=<value optimized out>, return_value=0xd37dc0, 
    return_value_ptr=<value optimized out>, this_ptr=<value optimized out>, 
    return_value_used=<value optimized out>) at /home/me/src/php-5.2.8/ext/mbstring/mbstring.c:2553
#5  0x000000000068608b in zend_do_fcall_common_helper_SPEC (execute_data=0x7fffdec7a6b0)
    at /home/me/src/php-5.2.8/Zend/zend_vm_execute.h:200
#6  0x00000000006763f3 in execute (op_array=0xd37268)
    at /home/me/src/php-5.2.8/Zend/zend_vm_execute.h:92
#7  0x0000000000658203 in zend_execute_scripts (type=8, retval=0x4, file_count=3)
    at /home/me/src/php-5.2.8/Zend/zend.c:1134
#8  0x00000000006184cb in php_execute_script (primary_file=0x7fffdec7cd20)
    at /home/me/src/php-5.2.8/main/main.c:2023
#9  0x00000000006d5a8c in main (argc=2, argv=0x7fffdec7cf18)
    at /home/me/src/php-5.2.8/sapi/cli/php_cli.c:1133