(app_push): Save saved_input in allocated buffer.
(app_pop): Restored saved_input.
(do_scrub_chars): Change get parameter to take char * and int as
arguments. Change GET macro to pass input_buffer to get
function. Don't save input into allocated buffer.
* as.h (do_scrub_chars): Update declaration.
* input-file.c (input_file_get): Change to take char * and int.
Read data into passed in buffer. Remove static buffer.
* read.c (scrub_from_string): Change to take char * and int. Copy
data into passed in buffer.
