check_and_emit_line(): rename and refactor

The function name was too bland and not explicit enough as to what it is
checking.  Split it into two, and call the one that checks if there is a
whitespace breakage "ws_check()", and call the other one that checks and
emits the line after color coding "ws_check_emit()".

Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/diff.c b/diff.c
index c00d633..52a34ee 100644
--- a/diff.c
+++ b/diff.c
@@ -535,9 +535,9 @@
 	else {
 		/* Emit just the prefix, then the rest. */
 		emit_line(ecbdata->file, set, reset, line, ecbdata->nparents);
-		(void)check_and_emit_line(line + ecbdata->nparents,
-		    len - ecbdata->nparents, ecbdata->ws_rule,
-		    ecbdata->file, set, reset, ws);
+		ws_check_emit(line + ecbdata->nparents,
+			      len - ecbdata->nparents, ecbdata->ws_rule,
+			      ecbdata->file, set, reset, ws);
 	}
 }
 
@@ -1153,8 +1153,7 @@
 	if (line[0] == '+') {
 		unsigned bad;
 		data->lineno++;
-		bad = check_and_emit_line(line + 1, len - 1,
-		    data->ws_rule, NULL, NULL, NULL, NULL);
+		bad = ws_check(line + 1, len - 1, data->ws_rule);
 		if (!bad)
 			return;
 		data->status |= bad;
@@ -1162,8 +1161,8 @@
 		fprintf(data->file, "%s:%d: %s.\n", data->filename, data->lineno, err);
 		free(err);
 		emit_line(data->file, set, reset, line, 1);
-		(void)check_and_emit_line(line + 1, len - 1, data->ws_rule,
-		    data->file, set, reset, ws);
+		ws_check_emit(line + 1, len - 1, data->ws_rule,
+			      data->file, set, reset, ws);
 	} else if (line[0] == ' ')
 		data->lineno++;
 	else if (line[0] == '@') {