patch 8.1.2062: the mouse code is spread out

Problem:    The mouse code is spread out.
Solution:   Move all the mouse code to mouse.c. (Yegappan Lakshmanan,
            closes #4959)
diff --git a/src/insexpand.c b/src/insexpand.c
index f472bca..eecc7f6 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -1995,7 +1995,7 @@
 	    }
 
 #ifdef FEAT_CINDENT
-	    want_cindent = (can_cindent_get() && cindent_on());
+	    want_cindent = (get_can_cindent() && cindent_on());
 #endif
 	    // When completing whole lines: fix indent for 'cindent'.
 	    // Otherwise, break line if it's too long.