Utility function and macro to copy Lisp string to C string.

Utility function and macro to copy Lisp string to C string.
* lisp.h (xlispstrdupa): New macro.
(xlispstrdup): New prototype.
* alloc.c (xlispstrdup): New function.
* callint.c (Fcall_interactively):
* fileio.c (Ffile_name_directory, Fexpand_file_name)
(Fsubstitute_in_file_name):
* frame.c (Fmake_terminal_frame): Use xlispstrdupa.
* image.c (x_create_bitmap_from_file):
* w32term.c (w32_term_init):
* xterm.c (x_term_init): Use xlispstrdup.