Shouldn't "char*" be "unsigned char*"?

[Dirk Laurie <dpl@...>]

Sorry for betraying my newbie-ness, this question was probably asked
fifteen years ago.

In the Lua API, Lua strings are mapped to C "char*".  Is this just a 
historical accident or a closely reasoned decision, such as that the 
convenience of the test "if (c<0)" to detect non-ASCII is more 
important than the inconvenience of occasional casts from "char*" to 
"unsigned char*"?

Dirk