Do not scan for coding declarations in open-file.

Do not scan for coding declarations in open-file.

* libguile/fports.c (scm_open_file): Do not scan for coding
  declarations.  Replace 'use_encoding' local variable with
  'binary'.  Update documentation string.

* module/ice-9/psyntax.scm (include): Add the same file-encoding
  logic that's used in compile-file and scm_primitive_load.

* module/ice-9/psyntax-pp.scm: Regenerate.

* doc/ref/api-io.texi (File Ports): Update docs.

* test-suite/tests/ports.test: Change "open-file HONORS file coding
  declarations" test to "open-file IGNORES file coding declaration".

* test-suite/tests/coding.test (scan-coding): Use 'file-encoding' to
  scan for the encoding, since 'open-input-file' no longer does so.