optim_doc: brent_line_min

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### 1.15 Linesearch, Brent method

Function File: [s,v,n] brent_line_min ( f,df,args,ctl )

  Line minimization of f along df

  Finds minimum of f on line x0 + dx*w | a < w < b by bracketing. a and b are passed through argument ctl.

  #### Arguments

  - f : string : Name of function. Must return a real value
  - args : cell : Arguments passed to f or RxC : f’s only argument. x0 must be at args{ ctl(2) }
  - ctl : 5 : (optional) Control variables, described below.

  #### Returned values

  - s : 1 : Minimum is at x0 + s*dx
  - v : 1 : Value of f at x0 + s*dx
  - nev : 1 : Number of function evaluations

  #### Control Variables

  - ctl(1) : Upper bound for error on s Default=sqrt(eps)
  - ctl(2) : Position of minimized argument in args Default= 1
  - ctl(3) : Maximum number of function evaluations Default= inf
  - ctl(4) : a Default=-inf
  - ctl(5) : b Default= inf

  Default values will be used if ctl is not passed or if nan values are given.