v4.8.0

• Support for Clang/LLVM 15.0.0

• Ast.character_kind and Ast.string_kind are now distinct
  types (aliases for Clang.clang_ext_characterkind and
  Clang.clang_ext_stringkind respectively.
  The constructor Ordinary replaced the former constructor Ascii
  for string_kind, to match the new convention used by
  clang::StringLiteral::StringKind from Clang 15.0.0.
  The constructor Ascii for character_kind is left unchanged.

• #1, #2: Ast.Var and Ast.Function constructors now have a storage
  field in addition to the computed linkage, exposing the value
  previously accessible via cursor_get_storage_class. The
  storage classes are now correctly printed by the printer.
  (reported by Ronan, rsaill/n47, #1)

• #3, #4: fix Clang.Expr.radix_of_integer_literal when the literal
  comes from a macro expansion, and fix printing of unsigned/long
  integer literals with Clang.Printer.
  (reported by Ronan, rsaill/n47, #3)