MdeModulePkg RegularExpressionDxe: Update Oniguruma from v6.9.0 to v6.9.3

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2066
Update Oniguruma to the latest version v6.9.3.
Oniguruma https://github.com/kkos/oniguruma
This release is the security fix release. It includes the changes:
Fixed CVE-2019-13224
Fixed CVE-2019-13225
Fixed many problems (found by libfuzzer programs)

Verify VS2015, GCC5 build.
Verify RegularExpressionProtocol GetInfo() and Match() function.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Cinnamon Shia <cinnamon.shia@hpe.com>
Signed-off-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>

MdeModulePkg/Universal/RegularExpressionDxe/Oniguruma/ascii.c

@@ -113,6 +113,6 @@ OnigEncodingType OnigEncodingASCII = {
   init,
   0, /* is_initialized */
   onigenc_always_true_is_valid_mbc_string,
-  ENC_FLAG_ASCII_COMPATIBLE,
+  ENC_FLAG_ASCII_COMPATIBLE|ENC_FLAG_SKIP_OFFSET_1,
   0, 0
 };