Fix quoting of copyright holders in configure.ac.

The old configure.ac did not work for a copyright holders string
containing commas due to insufficient quoting.  The new one allows this.
While this is, of course, not of direct consequence to the current code
(where the string is "Bitcoin Core"), it should still be fixed now that
the string is actually factored out.

configure.ac

@@ -7,7 +7,7 @@ define(_CLIENT_VERSION_BUILD, 0)
 define(_CLIENT_VERSION_IS_RELEASE, false)
 define(_COPYRIGHT_YEAR, 2016)
 define(_COPYRIGHT_HOLDERS,[The %s developers])
-define(_COPYRIGHT_HOLDERS_SUBSTITUTION,[Bitcoin Core])
+define(_COPYRIGHT_HOLDERS_SUBSTITUTION,[[Bitcoin Core]])
 AC_INIT([Bitcoin Core],[_CLIENT_VERSION_MAJOR._CLIENT_VERSION_MINOR._CLIENT_VERSION_REVISION],[https://github.com/bitcoin/bitcoin/issues],[bitcoin],[https://bitcoincore.org/])
 AC_CONFIG_SRCDIR([src/main.cpp])
 AC_CONFIG_HEADERS([src/config/bitcoin-config.h])
@@ -999,10 +999,10 @@ AC_DEFINE(CLIENT_VERSION_MINOR, _CLIENT_VERSION_MINOR, [Minor version])
 AC_DEFINE(CLIENT_VERSION_REVISION, _CLIENT_VERSION_REVISION, [Build revision])
 AC_DEFINE(CLIENT_VERSION_BUILD, _CLIENT_VERSION_BUILD, [Version Build])
 AC_DEFINE(CLIENT_VERSION_IS_RELEASE, _CLIENT_VERSION_IS_RELEASE, [Version is release])
-AC_DEFINE(COPYRIGHT_YEAR, _COPYRIGHT_YEAR, [Version is release])
+AC_DEFINE(COPYRIGHT_YEAR, _COPYRIGHT_YEAR, [Copyright year])
 AC_DEFINE(COPYRIGHT_HOLDERS, "_COPYRIGHT_HOLDERS", [Copyright holder(s) before %s replacement])
 AC_DEFINE(COPYRIGHT_HOLDERS_SUBSTITUTION, "_COPYRIGHT_HOLDERS_SUBSTITUTION", [Replacement for %s in copyright holders string])
-define(_COPYRIGHT_HOLDERS_FINAL, patsubst(_COPYRIGHT_HOLDERS, [%s], [_COPYRIGHT_HOLDERS_SUBSTITUTION]))
+define(_COPYRIGHT_HOLDERS_FINAL, [patsubst(_COPYRIGHT_HOLDERS, [%s], [_COPYRIGHT_HOLDERS_SUBSTITUTION])])
 AC_DEFINE(COPYRIGHT_HOLDERS_FINAL, "_COPYRIGHT_HOLDERS_FINAL", [Copyright holder(s)])
 AC_SUBST(CLIENT_VERSION_MAJOR, _CLIENT_VERSION_MAJOR)
 AC_SUBST(CLIENT_VERSION_MINOR, _CLIENT_VERSION_MINOR)