Bug in SPEC (for Lfindzero=1) about spec HOT 5 CLOSED

@jloizu Could you give / point out a test case? I will check this.

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Here is an input file that does not work (Lfindzero=1) but does work if you set Lfindzero=2.

M=4.N=0.Lcon=0.Lfree=0.sp.txt

(you have to remove the txt extension)

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In minpack subroutine "hybrd", the function-to-optimize, "fcn1", is called with value irevcm=2. The logic of "fcn1" is that if irevcm=0 or 1, it works normally, otherwise returns an error.
Careful inspection shows "fcn1" should not report an error but should work exactly the same as irevcm=1. This happens when "fdjac1", the subroutine calculates the derivatives using forward finite difference, passes irevcm=2 to "fcn1".
A quick fix will be making "fcn1" do the same job in =1 and =2 case.
I have pushed a new branch, Lfindzero-fix, and created a pull request. Tests are welcome before merging.

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Sorry, I was distracted by other things. zhisong's fix should work, but I cannot test it in a quick time. I don't have a valid environmental file on PPPL cluster to compile & run SPEC (the current one I have somehow doesn't work).
The variable irevcm is historic and was used for NAG C05PDF & C05NDF. When I replaced the two NAG subroutines by hybrd & hybrj in MINPACK, I used irevcm to play as iflag need by MINPACK subroutines.

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Yes Zhisong's fix seems to solve the problem! I tested the branch and everything looks good. I am now merging it into master.

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