Add a way to disable the deprecation warning.

.hoerc

@@ -1,2 +1,2 @@
 --- 
-exclude: !ruby/regexp /(?:\.(hg|hoe|bundle|irb|pry|ruby-(version|gemset)|gems|tm|DS_Store|travis\.yml)|sample|tmp|certs|build|lib/.*(so|dll)|appveyor\.yml|misc|Gemfile|pg\.gemspec)/
+exclude: !ruby/regexp /(?:\.(hg|hoe|bundle|irb|pry|ruby-(version|gemset)|gems|tm|DS_Store|travis\.yml)|sample|vendor|tmp|certs|build|lib/.*(so|dll)|appveyor\.yml|misc|Gemfile|pg\.gemspec)/

lib/pg/deprecated_constants.rb

@@ -2,18 +2,21 @@
 #encoding: utf-8
 
 # Warn about use of deprecated constants when this is autoloaded
-callsite = caller(3).first
+unless ENV['PG_SKIP_DEPRECATION_WARNING']
+	callsite = caller(3).first
 
-warn <<END_OF_WARNING
+	warn <<-END_OF_WARNING
 The PGconn, PGresult, and PGError constants are deprecated, and will be
 removed as of version 1.0.
 
 You should use PG::Connection, PG::Result, and PG::Error instead, respectively.
 
-Called from #{callsite}
-END_OF_WARNING
-
+You can disable this warning by setting the PG_SKIP_DEPRECATION_WARNING environment
+variable.
 
+Called from #{callsite}
+	END_OF_WARNING
+end
 
 PGconn   = PG::Connection
 PGresult = PG::Result