This macro establishes local alien variables with the specified
Alien types and names for dynamic extent of the body. The variable
names are established as symbol-macros; the bindings have
lexical scope, and may be assigned with setq or setf.
This form is analogous to defining a local variable in C: additional
storage is allocated, and the initial value is copied.
with-alien also establishes a new scope for named structures
and unions. Any type specified for a variable may contain
name structure or union types with the slots specified. Within the
lexical scope of the binding specifiers and body, a locally defined
structure type foo can be referenced by its name using:
(struct foo)