Returns a printable version of +self+, enclosed in double-quotes.

Most printable characters are rendered simply as themselves:

  'abc'.inspect        # => "\"abc\""
  '012'.inspect        # => "\"012\""
  ''.inspect           # => "\"\""
  "\u000012".inspect   # => "\"\\u000012\""
  'こんにちは'.inspect  # => "\"こんにちは\""

But printable characters double-quote (<tt>'"'</tt>) and backslash and (<tt>'\\'</tt>) are escaped:

  '"'.inspect  # => "\"\\\"\""
  '\\'.inspect # => "\"\\\\\""

Unprintable characters are the {ASCII characters}[https://en.wikipedia.org/wiki/ASCII]
whose values are in range <tt>0..31</tt>,
along with the character whose value is +127+.

Most of these characters are rendered thus:

  0.chr.inspect # => "\"\\x00\""
  1.chr.inspect # => "\"\\x01\""
  2.chr.inspect # => "\"\\x02\""
  # ...

A few, however, have special renderings:

  7.chr.inspect  # => "\"\\a\""  # BEL
  8.chr.inspect  # => "\"\\b\""  # BS
  9.chr.inspect  # => "\"\\t\""  # TAB
  10.chr.inspect # => "\"\\n\""  # LF
  11.chr.inspect # => "\"\\v\""  # VT
  12.chr.inspect # => "\"\\f\""  # FF
  13.chr.inspect # => "\"\\r\""  # CR
  27.chr.inspect # => "\"\\e\""  # ESC

Related: see {Converting to Non-String}[rdoc-ref:String@Converting+to+Non-String].
