crlf: update to match git's logic

Examine the recent CRLF changes to git by Torsten Bögershausen and
include similar changes to update our CRLF logic to match.

Note: Torsten Bögershausen has previously agreed to allow his changes to
be included in libgit2.

src/buf_text.c

@@ -310,6 +310,7 @@ bool git_buf_text_gather_stats(
 			}
 	}
 
-	return (stats->nul > 0 ||
+	/* Treat files with a bare CR as binary */
+	return (stats->cr != stats->crlf || stats->nul > 0 ||
 		((stats->printable >> 7) < stats->nonprintable));
 }

src/filter.h

@@ -15,16 +15,6 @@
 /* Amount of file to examine for NUL byte when checking binary-ness */
 #define GIT_FILTER_BYTES_TO_CHECK_NUL 8000
 
-/* Possible CRLF values */
-typedef enum {
-	GIT_CRLF_GUESS = -1,
-	GIT_CRLF_BINARY = 0,
-	GIT_CRLF_TEXT,
-	GIT_CRLF_INPUT,
-	GIT_CRLF_CRLF,
-	GIT_CRLF_AUTO,
-} git_crlf_t;
-
 typedef struct {
 	git_attr_session *attr_session;
 	git_buf *temp_buf;