Clarification of borrowck (#354)

Author: Arthur-Milchior

src/borrow-splitting.md

@@ -1,10 +1,10 @@
 # Splitting Borrows
 
 The mutual exclusion property of mutable references can be very limiting when
-working with a composite structure. The borrow checker understands some basic
-stuff, but will fall over pretty easily. It does understand structs
-sufficiently to know that it's possible to borrow disjoint fields of a struct
-simultaneously. So this works today:
+working with a composite structure. The borrow checker (a.k.a. borrowck)
+understands some basic stuff, but will fall over pretty easily. It does
+understand structs sufficiently to know that it's possible to borrow disjoint
+fields of a struct simultaneously. So this works today:
 
 ```rust
 struct Foo {