Description:
------------
On 5.5.0-x64, these 2 tests crash, with and without opcache

Test script:
---------------
ext/mbstring/tests/mb_eregi.phpt
ext/mbstring/tests/mb_eregi_invalid_arguments.phpt

Expected result:
----------------
Test Pass

Actual result:
--------------
Crash here:

00000000`008ce338 000007fe`e309fe79 php_mbstring!code2_hash [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\oniguruma\enc\unicode.c @ 10860]
00000000`008ce340 000007fe`e30a23fc php_mbstring!onig_st_add_direct+0x29 [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\oniguruma\st.c @ 309]
00000000`008ce370 000007fe`e30a3038 php_mbstring!init_case_fold_table+0x12c [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\oniguruma\enc\unicode.c @ 10937]
00000000`008ce3a0 000007fe`e30a45bd php_mbstring!onigenc_unicode_get_case_fold_codes_by_str+0x58 [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\oniguruma\enc\unicode.c @ 11169]
00000000`008ce4a0 000007fe`e3074d9b php_mbstring!get_case_fold_codes_by_str+0x1d [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\oniguruma\enc\utf8.c @ 286]
00000000`008ce4e0 000007fe`e3074907 php_mbstring!expand_case_fold_string+0x7b [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\oniguruma\regcomp.c @ 3388]
00000000`008ce6a0 000007fe`e3076a69 php_mbstring!setup_tree+0xb7 [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\oniguruma\regcomp.c @ 3899]
00000000`008ce6f0 000007fe`e3076f70 php_mbstring!onig_compile+0xc9 [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\oniguruma\regcomp.c @ 5336]
00000000`008ce820 000007fe`e30a5d50 php_mbstring!onig_new+0x70 [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\oniguruma\regcomp.c @ 5546]
00000000`008ce860 000007fe`e30a48ce php_mbstring!php_mbregex_compile_pattern+0xd0 [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\php_mbregex.c @ 458]
00000000`008ce990 000007fe`e30a658b php_mbstring!_php_mb_regex_ereg_exec+0x1de [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\php_mbregex.c @ 728]
00000000`008cea20 000007fe`e356fbe2 php_mbstring!zif_mb_eregi+0x1b [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\ext\mbstring\php_mbregex.c @ 783]
00000000`008cea70 000007fe`e356eafa php5ts!zend_do_fcall_common_helper_SPEC+0x272 [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\zend\zend_vm_execute.h @ 548]
00000000`008ceb30 000007fe`e35b302e php5ts!execute_ex+0x7a [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\zend\zend_vm_execute.h @ 356]
00000000`008ceba0 000007fe`e35b2a2c php5ts!zend_execute+0x4be [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\zend\zend_vm_execute.h @ 382]
00000000`008cec00 000007fe`e35b25d9 php5ts!zend_execute_scripts+0x19c [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\zend\zend.c @ 1317]
00000000`008cecc0 00000001`3f19248f php5ts!php_execute_script+0x209 [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\main\main.c @ 2479]
00000000`008cf080 00000001`3f1933a5 php!do_cli+0x9df [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\sapi\cli\php_cli.c @ 994]
00000000`008cf590 00000001`3f19b683 php!main+0x655 [c:\php-sdk\snap_5_5\vc11\x64\ts-windows-vc11-x64\sapi\cli\php_cli.c @ 1377]
00000000`008cf790 00000000`7700f56d php!__tmainCRTStartup+0x10f [f:\dd\vctools\crt_bld\self_64_amd64\crt\src\crtexe.c @ 536]
00000000`008cf7c0 00000000`77143281 kernel32!BaseThreadInitThunk+0xd
00000000`008cf7f0 00000000`00000000 ntdll!RtlUserThreadStart+0x21