BUG/MINOR: tools: my_memspn/my_memcspn wrong cast causing incorrect byte reading

BUG/MINOR: tools: my_memspn/my_memcspn wrong cast causing incorrect byte reading

Both functions cast void * to int * and dereference, reading 4 bytes as an
integer instead of a single byte. This is passed to memchr() which expects a
byte value. On unaligned addresses this causes crashes on ARM/mips etc, and
search for the wrong byte on big endian platforms. Fixed to cast to
const unsigned char * and dereference a single byte. This is marked as
minor because these functions were added in 2.2 by commit 5eb96cbcbc
("MINOR: standard: Add my_memspn and my_memcspn") and have not been used
since then.