merge 4.2 updates from the branch

diff --cc BUILD.md
Simple merge

diff --cc README.md
Simple merge

diff --cc configure.ac
index 8d3a156397d023d603960e9b8a0a19487415de94,41cd613f1519234a09f33ccb01f17be216092128..1e58765fce13e2583fbd712182e5fd42e10f220b
--- 1/configure.ac
--- 2/configure.ac
+++ b/configure.ac
@@@ -2,7 -2,7 +2,7 @@@
  # Process this file with autoconf to produce a configure script.
  
  AC_PREREQ([2.50])
- AC_INIT([shairport-sync], [4.1.1], [4265913+mikebrady@users.noreply.github.com])
 -AC_INIT([shairport-sync], [4.1-dev], [4265913+mikebrady@users.noreply.github.com])
++AC_INIT([shairport-sync], [4.2rc0], [4265913+mikebrady@users.noreply.github.com])
  AM_INIT_AUTOMAKE([subdir-objects])
  AC_CONFIG_SRCDIR([shairport.c])
  AC_CONFIG_HEADERS([config.h])