xpath abbreviate: add support for string literal that contains double-quote

[pulver]

This adds support for a string literal that contains a double-quote to XPathParser#abbreviate. Basically any literal that contains a double-quote " must be quoted by single-quotes ' since XPath 1.0 does not support any escape characters.

The change improves the following test script

require 'rexml'

parsed = REXML::Parsers::XPathParser.new.parse('/a[b/text()=concat("c\'",\'"d\')]')
puts "#{parsed}"
puts ""
appreviated = REXML::Parsers::XPathParser.new.abbreviate parsed
puts "#{appreviated}"

Output Before Change

[:document, :child, :qname, "", "a", :predicate, [:eq, [:child, :qname, "", "b", :child, :text], [:function, "concat", [[:literal, "c'"], [:literal, "\"d"]]]]]

/a[ b/text() = concat( "c'" , "\"d" ) ]

Output After Change

[:document, :child, :qname, "", "a", :predicate, [:eq, [:child, :qname, "", "b", :child, :text], [:function, "concat", [[:literal, "c'"], [:literal, "\"d"]]]]]

/a[ b/text() = concat( "c'" , '"d' ) ]

[kou]

Does this work with a number literal?

[pulver]

Good catch, thank you. I restored the previous method of literal.inspect for all non-Strings.

I wasn't sure how to handle this literal translation so I left it as it was:

rexml/lib/rexml/parsers/xpathparser.rb

Lines 86 to 87 in 54b7109

	when :literal
	string << %Q{ "#{path.shift}" }

[kou]

Could you use snake_case?

Suggested change

	def QuoteLiteral literal
	def quote_literal(literal)

[kou]

And could you move this method to before #LocalPath (the line 192)?
Method in #LocationPath to #FunctionCall are for syntaxes in XPath. I don't want to mix this and them.

[kou]

Suggested change

	# Xpath 1.0 does not support escape characters.
	# XPath 1.0 does not support escape characters.

[kou]

Could you use string interpolation instead of String#%?

Suggested change

	pattern = literal.include?('"') ? "'%s'" : '"%s"'
	pattern % literal
	if literal.include?("'")
	"\"#{literal}\""
	else
	"'#{literal}'"
	end

[pulver]

Done, thanks for the feedback.

[kou]

Could you move this private above quote_literal?

[pulver]

Done: d6a02b9