Reorder chapters + put abstract into frontmatter

chapters/02_background/listings/classificationmarkers.cpp

@@ -0,0 +1,6 @@
+// Continuation of previous example
+if (sum == 100) {
+  fail_marker_positive();
+} else {
+  fail_marker_negative();
+}

chapters/02_background/listings/tracefence.cpp

@@ -0,0 +1,8 @@
+fail_start_trace();
+
+int sum = 0;
+for (int i = 0; i < 100; ++i) {
+  ++sum;
+}
+
+fail_stop_trace();

chapters/02_background/listings/wat_example.hex

@@ -0,0 +1,5 @@
+0000000 6100 6d73 0001 0000 0501 6001 0100 037f
+0000010 0102 0500 0103 0200 0806 7f01 4101 8880
+0000020 0b04 1107 0602 656d 6f6d 7972 0002 6d04
+0000030 6961 006e 0a00 0106 0004 2a41 000b     
+000003d

chapters/02_background/listings/wat_example.wat

@@ -0,0 +1,8 @@
+(module $wat_example.wasm
+  (type (;0;) (func (result i32)))
+  (func $main (type 0) (result i32)
+    i32.const 42)
+  (memory (;0;) 2)
+  (global $__stack_pointer (mut i32) (i32.const 66560))
+  (export "memory" (memory 0))
+  (export "main" (func $main)))