wpm : portable unicode tolower (#6305)

Also use C locale for ispunct/isspace, and split unicode-data.cpp from unicode.cpp.

Package.swift

@@ -32,6 +32,7 @@ let package = Package(
                 "ggml.c",
                 "llama.cpp",
                 "unicode.cpp",
+                "unicode-data.cpp",
                 "ggml-alloc.c",
                 "ggml-backend.c",
                 "ggml-quants.c",