scripted-diff: Rename PACKAGE_* variables to CLIENT_*

This change ensures consistent use of the `CLIENT_` namespace everywhere
in the repository.

-BEGIN VERIFY SCRIPT-

ren() { sed -i "s/\<$1\>/$2/g" $( git grep -l "$1" ./cmake ./src :\(exclude\)./src/secp256k1 ./test ) ; }

ren PACKAGE_NAME      CLIENT_NAME
ren PACKAGE_VERSION   CLIENT_VERSION_STRING
ren PACKAGE_URL       CLIENT_URL
ren PACKAGE_BUGREPORT CLIENT_BUGREPORT

-END VERIFY SCRIPT-

test/config.ini.in

@@ -6,8 +6,8 @@
 # test/*/test_runner.py and test/util/rpcauth-test.py
 
 [environment]
-PACKAGE_NAME=@CLIENT_NAME@
-PACKAGE_BUGREPORT=@CLIENT_BUGREPORT@
+CLIENT_NAME=@CLIENT_NAME@
+CLIENT_BUGREPORT=@CLIENT_BUGREPORT@
 SRCDIR=@abs_top_srcdir@
 BUILDDIR=@abs_top_builddir@
 EXEEXT=@EXEEXT@