to be included into this one. This works the same way as #include
does in C; as far as the user is concerned, the included file is
inlined into the current one.
Since config(8) is no longer limited to working on one user-supplied
file, printing just a line number in an error message is not
sufficient. The new global variable yyfile represents the file
currently being parsed, and must be printed as well.
Reviewed by: imp
Obtained from: OpenBSD
b5164c6585