unescape: fix casting char to uint32_t on arm inconsistent with x86
unescape: fix casting char to uint32_t on arm inconsistent with x86

This patch fix casting issue where casting char to uint32_t on arm is
inconsistent with x86, because char is unsigned char by default on arm,
but signed char on x86, so need to do a explicit conversion before casting
char to uint32_t.

Signed-off-by: Yinjie Du <d9ddf4634d12b47eedc351bf2c9c31ea6421733f@smartx.com>

fluent/fluent-bit,nokute78/fluent-bit,fluent/fluent-bit,fluent/fluent-bit,nokute78/fluent-bit,nokute78/fluent-bit,fluent/fluent-bit,nokute78/fluent-bit,nokute78/fluent-bit,fluent/fluent-bit,nokute78/fluent-bit,fluent/fluent-bit,fluent/fluent-bit,nokute78/fluent-bit,nokute78/fluent-bit,nokute78/fluent-bit,nokute78/fluent-bit,nokute78/fluent-bit,fluent/fluent-bit,fluent/fluent-bit,fluent/fluent-bit,nokute78/fluent-bit,fluent/fluent-bit,fluent/fluent-bit