Enforce function declaration format in bash8

Check that function calls look like ^function foo {$ in bash8, and fix
all existing failures of that check.  Add a note to HACKING.rst

Change-Id: Ic19eecb39e0b20273d1bcd551a42fe400d54e938
diff --git a/tools/copy_dev_environment_to_uec.sh b/tools/copy_dev_environment_to_uec.sh
index 3fd4423..94a4926 100755
--- a/tools/copy_dev_environment_to_uec.sh
+++ b/tools/copy_dev_environment_to_uec.sh
@@ -22,7 +22,7 @@
 source ./stackrc
 
 # Echo usage
-usage() {
+function usage {
     echo "Add stack user and keys"
     echo ""
     echo "Usage: $0 [full path to raw uec base image]"