Tweak tparam.c and tgoto.c.

Tweak tparam.c and tgoto.c.

(tparam.c): Use ANSI-style declarations.  Include relevant headers.
Use memcpy rather than bcopy.  Check for malloc and realloc failures.

(tterm.c): Check for tparam and tgoto failures.  Handle the case
where tparam and tgoto malloc their own memory.  Ensure that a Scheme
interrupt/GC in char_pointer_to_string does not leak that memory.