Rollup merge of #22393 - kmcallister:macros-chapter , r=steveklabnik

This is a more introductory document, suitable for Part II. The arcane details move to an "Advanced macros" chapter in Part III.

Conflicts:
	src/doc/trpl/macros.md

diff --cc src/doc/trpl/SUMMARY.md
index 9e16414d225a98e5f9ad636503e726457624c47d,e8e9c28a783eb16e5cc1ef20e10ecce51d599f26..d57aff7f4f411fbc9974666127a02150b324301d
--- 1/src/doc/trpl/SUMMARY.md
--- 2/src/doc/trpl/SUMMARY.md
+++ b/src/doc/trpl/SUMMARY.md
@@@ -34,7 -35,6 +35,7 @@@
  * [III: Advanced Topics](advanced.md)
      * [FFI](ffi.md)
      * [Unsafe Code](unsafe.md)
-     * [Macros](macros.md)
+     * [Advanced Macros](advanced-macros.md)
      * [Compiler Plugins](plugins.md)
  * [Conclusion](conclusion.md)
 +* [Glossary](glossary.md)