Support converting between I;16N and L

Author: radarhere

Tests/test_mode_i16.py

@@ -90,10 +90,7 @@ def test_convert():
 
     im = original.copy()
 
-    verify(im.convert("I;16"))
-    verify(im.convert("I;16").convert("L"))
-    verify(im.convert("I;16").convert("I"))
-
-    verify(im.convert("I;16B"))
-    verify(im.convert("I;16B").convert("L"))
-    verify(im.convert("I;16B").convert("I"))
+    for mode in ("I;16", "I;16B", "I;16N"):
+        verify(im.convert(mode))
+        verify(im.convert(mode).convert("L"))
+        verify(im.convert(mode).convert("I"))

src/libImaging/Convert.c

@@ -970,6 +970,13 @@ static struct {
     {"I;16L", "L", I16L_L},
     {"L", "I;16B", L_I16B},
     {"I;16B", "L", I16B_L},
+#ifdef WORDS_BIGENDIAN
+    {"L", "I;16N", L_I16B},
+    {"I;16N", "L", I16B_L},
+#else
+    {"L", "I;16N", L_I16L},
+    {"I;16N", "L", I16L_L},
+#endif
 
     {"I;16", "F", I16L_F},
     {"I;16L", "F", I16L_F},