fix test-mq-eol under --pure (mimic diffhelper.c behaviour)

bug discovered by apycot (apycot.hg-scm.org)

mercurial/pure/diffhelpers.py

@@ -34,11 +34,15 b' def addlines(fp, hunk, lena, lenb, a, b)'
 
 def fix_newline(hunk, a, b):
     l = hunk[-1]
-    c = l[0]
+    # tolerate CRLF in last line
+    if l.endswith('\r\n'):
+        hline = l[:-2]
+    else:
     hline = l[:-1]
+    c = hline[0]
 
     if c == " " or c == "+":
-        b[-1] = l[1:-1]
+        b[-1] = hline[1:]
     if c == " " or c == "-":
         a[-1] = hline
     hunk[-1] = hline