Allow inclusion of binary files outside of the debian subdirectory

Allow inclusion of binary files outside of the debian subdirectory

* scripts/Dpkg/ErrorHandling.pm (errormsg): New function displaying
an error message to stderr without dying.
* scripts/Dpkg/Source/Patch.pm (add_diff_file): Add a hook in the
handling of modified binary files. Don't fail unconditionnaly when a
binary file is detected. Return a value indicating if the diff
call succeeded.
(add_diff_directory): Don't display some warnings (that apply only to
files whose changes can be represented in diff) for modified
binary files.
(_fail_with_msg, _fail_not_same_type): Use new errormsg() function.
* scripts/Dpkg/Source/Package/V2_0.pm (do_extract): Extract the debian
tarball "in-place" so that it can contain other files besides the debian
sub-directory.
(do_build): Handle modified binary files. They are added to the debian
tarball if --include-binaries is used, or if they are whitelisted in
debian/source/include-binaries. The usage of --include-binaries will
modify debian/source/include-binaries if needed.
* man/dpkg-source.1: Update manual page accordingly.