Since the code is identical when just checking if a utility is present on
the system or not, we can factorize it.

Signed-off-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>

* src/patch.c (main): Say that we are checking a file and not that we are
patching it in --dry-run mode.  Don't say "saving rejects to file" when we
don't create reject files.
* tests/reject-format: Add rejects with --dry-run test case.
* tests/bad-filenames, tests/fifo, tests/mixed-patch-types: Update.

* tests/copy-rename, tests/criss-cross, tests/file-modes,
tests/mixed-patch-types, tests/quoted-filenames: Add missing index lines in the
"dif --git" test cases: We will use some of them for consistency checks soon.

In git-style patch files, all patches refer to the initial state of the input
files; files cannot be modified more than once.  Implement these semantics by
creating all output files once all patches in the patch file have been
processed.
* src/patch.c (init_files_to_output, output_files): Add prototypes.
(main): Remember which type of patch file we are processing.  Initialize the
output files list.  Output files of git-style patches once all patches have
been read, or when from git-style to normal patches.
(file_to_output): New struct.
(files_to_output): List of the files to output.
(output_file, output_file_now, output_file_later): Either queue a file for
deletion, remember to output a file later (git-style), or output the file
immediately (normal).
(dispose_file_to_output, init_files_to_output, output_files,
 forget_output_files): New functions.
(gl_list_clear): Should be provided by gnulib but isn't.
(cleanup): Clean up any left-over temporary output files as well.
* tests/Makefile-am (XFAIL_TESTS): Remove criss-cross; this test case works now.
* tests/mixed-patch-types: Patch files that change from normal to git-style, or
from git-style to normal.