Return string with escape sequences substituted by values.  Some
escape sequences take arguments.  You can specify arguments inside
“{}” immediately following the escape sequence.
     The escape sequences you can pass to this function are:
          
- \\
- Substitute a backslash. 
 
- \e
- Substitute an ESC character. 
 
- \f
- Substitute the selected frame; an argument names a frame parameter. 
 
- \n
- Substitute a newline. 
 
- \p
- Substitute a parameter's value; the argument names the parameter. 
 
- \r
- Substitute a carriage return. 
 
- \t
- Substitute the selected thread; an argument names a thread parameter. 
 
- \v
- Substitute the version of GDB. 
 
- \w
- Substitute the current working directory. 
 
- \[
- Begin a sequence of non-printing characters.  These sequences are
typically used with the ESC character, and are not counted in the string
length.  Example: “\[\e[0;34m\](gdb)\[\e[0m\]” will return a
blue-colored “(gdb)” prompt where the length is five. 
 
- \]
- End a sequence of non-printing characters. 
For example:
     
          substitute_prompt (``frame: \f,
                             print arguments: \p{print frame-arguments}'')
     
will return the string:
     
          "frame: main, print arguments: scalars"