Include getopt.h. Add some extern decls.

Include getopt.h.  Add some extern decls.
(safegetc): New function to deal with EOF gracefully.
(literalchar); new function to deal with reading \ escapes.
(lex): Use literalchar.
(lex): Implemented "..." tokens.
(literalchar, lex, parse_percent_token): Made tokenbuffer
always contain the token.  This includes growing the token
buffer while reading an integer.
(parse_percent_token): Replaced if-else statement with percent_table.
(parse_percent_token): Added % declarations as another
way to specify the flags -n, -l, and -r.  Also added hooks for
-d, -k, -y, -v, -t, -p, -b, -o, but implementation requires
major changes to files.c.
(lex) Retain in the incoming stream a character following
an incorrect '/'.
(skip_white_space, lex):  Revised most error messages
and changed fatal to warn to avoid aborting.
(percent_table):  Added %thong declarations.