Update books

rust-lang · Centril · Feb 24, 2020 · Feb 24, 2020 · Feb 24, 2020 · Feb 28, 2020
commit 8ea676eccaa3596c56b5bf665a1adb155b634ff3
diff --git a/src/doc/embedded-book b/src/doc/embedded-book
diff --git a/src/doc/nomicon b/src/doc/nomicon
diff --git a/src/doc/reference b/src/doc/reference
diff --git a/src/doc/rust-by-example b/src/doc/rust-by-example
+19 −0		src/intro/index.md
+1 −1		src/static-guarantees/design-contracts.md
+1 −1		src/attributes.md
+1 −1		src/behavior-considered-undefined.md
+3 −3		src/const_eval.md
+1 −1		src/expressions/array-expr.md
+5 −5		src/items/associated-items.md
+1 −1		src/items/enumerations.md
+1 −1		src/items/use-declarations.md
+25 −3		src/type-layout.md