1.0.1 warnings - recommended code uses inconsistent capitalized constants

从 lib/uri/common.rb 和 lib/uri/rfc3986_parser.rb 中的警告定义开始，使用 issue 的 git grep 结果检查每条建议。检查现有常量的定义方式，并确定要公开的一致大写形式。当警告建议使用大小写一致的常量，且不会混淆 parser 和 parser-class 的名称时，即表示完成。

@hsbt First of all, thank you again for your work on ruby.

Following up on #125. The "suggested" or recommended code in the warnings can be confusing:

% ruby -W2 -e "puts RUBY_VERSION; require 'uri'; puts URI::VERSION; puts URI::PATTERN; URI::DEFAULT_PARSER.escape(''); URI::DEFAULT_PARSER.unescape(''); puts URI::Regexp; puts URI::REGEXP"
3.1.6
1.0.1
-e:1: warning: URI::PATTERN is obsolete. Use RFC2396_Parser::PATTERN explicitly.
URI::RFC2396_REGEXP::PATTERN
-e:1: warning: URI::RFC3986_PARSER.escape is obsoleted. Use URI::RFC2396_PARSER.escape explicitly.
-e:1: warning: URI::RFC3986_PARSER.unescape is obsoleted. Use URI::RFC2396_PARSER.unescape explicitly.
-e:1: warning: URI::Regexp is obsolete. Use RFC2396_Parser::Regexp explicitly.
Regexp
-e:1: warning: URI::REGEXP is obsolete. Use URI::RFC2396_REGEXP explicitly.
URI::RFC2396_REGEXP

The problem is this:
RFC2396_Parser vs. RFC2396_PARSER or RFC2396_Parser::Regexp vs. URI::RFC2396_REGEXP

It's easy to make a mistake and use the wrong case. They're very similar names with different capitalization but they're not the same thing. I'm sure there are others:

% git grep "explicitly" lib/uri*
lib/uri/common.rb:      warn "URI::REGEXP is obsolete. Use URI::RFC2396_REGEXP explicitly.", uplevel: 1 if $VERBOSE
lib/uri/common.rb:      warn "URI::#{const} is obsolete. Use RFC2396_PARSER.regexp[#{const.inspect}] explicitly.", uplevel: 1 if $VERBOSE
lib/uri/common.rb:      warn "URI::#{const} is obsolete. Use RFC2396_Parser::#{const} explicitly.", uplevel: 1 if $VERBOSE
lib/uri/rfc3986_parser.rb:      warn "URI::RFC3986_PARSER.extract is obsoleted. Use URI::RFC2396_PARSER.extract explicitly.", uplevel: 1 if $VERBOSE
lib/uri/rfc3986_parser.rb:      warn "URI::RFC3986_PARSER.make_regexp is obsoleted. Use URI::RFC2396_PARSER.make_regexp explicitly.", uplevel: 1 if $VERBOSE
lib/uri/rfc3986_parser.rb:      warn "URI::RFC3986_PARSER.escape is obsoleted. Use URI::RFC2396_PARSER.escape explicitly.", uplevel: 1 if $VERBOSE
lib/uri/rfc3986_parser.rb:      warn "URI::RFC3986_PARSER.unescape is obsoleted. Use URI::RFC2396_PARSER.unescape explicitly.", uplevel: 1 if $VERBOSE

Can we add capitalized versions of constants so we can consistently suggest capitalized versions of constants in these warnings?

Thank you!