Bug(Map): Default value shouldn't be overwritten in USAGE

[wjrforcyber]

Default value in usage manual shouldn't be changed when wrong parameter value is given.
When a wrong value such as -50000 set to Gain, the default value is overwritten by this wrong value:

ABC command line: "source -x ./testsplit.script".

abc - > read_aiger i10.aig
abc - > read_lib NangateOpenCellLibrary_typical.lib
Library "NangateOpenCellLibrary" from "NangateOpenCellLibrary_typical.lib" has 90 cells (35 skipped: 21 seq; 6 tri-state; 8 no func; 10 dont_use).  Time =     0.04 sec
Warning: Detected 2 multi-output gates (for example, "FA_X1").
abc - > strash
abc - > resub -K 6 -N 3
abc - > resub -K 8 -N 3
abc - > resub -K 10 -N 3
abc - > map -G -50000
usage: map [-DABFSG float] [-M num] [-arspfuovh]
                   performs standard cell mapping of the current network
        -D float : sets the global required times [default = not used]
        -A float : "area multiplier" to bias gate selection [default = 0.00]
        -B float : "delay multiplier" to bias gate selection [default = 0.00]
        -F float : the logarithmic fanout delay parameter [default = 0.00]
        -S float : the slew parameter used to generate the library [default = 0.00]
        -G float : the gain parameter used to generate the library [default = -50000.00]
        -M num   : skip gate classes whose size is less than this [default = 0]
        -a       : toggles area-only mapping [default = no]
        -r       : toggles area recovery [default = yes]
        -s       : toggles sweep after mapping [default = no]
        -p       : optimizes power by minimizing switching [default = no]
        -f       : do not use large gates to map high-fanout nodes [default = no]
        -u       : use standard-cell profile [default = no]
        -o       : toggles using buffers to decouple combinational outputs [default = no]
        -v       : toggles verbose output [default = no]
        -h       : print the command usage
** cmd error: aborting 'source ./testsplit.script'

A temp variable to save the default value is proposed here.

ABC command line: "source -x ./testsplit.script".

abc - > read_aiger i10.aig
abc - > read_lib NangateOpenCellLibrary_typical.lib
Library "NangateOpenCellLibrary" from "NangateOpenCellLibrary_typical.lib" has 90 cells (35 skipped: 21 seq; 6 tri-state; 8 no func; 10 dont_use).  Time =     0.04 sec
Warning: Detected 2 multi-output gates (for example, "FA_X1").
abc - > strash
abc - > resub -K 6 -N 3
abc - > resub -K 8 -N 3
abc - > resub -K 10 -N 3
abc - > map -G -50000
usage: map [-DABFSG float] [-M num] [-arspfuovh]
                   performs standard cell mapping of the current network
        -D float : sets the global required times [default = not used]
        -A float : "area multiplier" to bias gate selection [default = 0.00]
        -B float : "delay multiplier" to bias gate selection [default = 0.00]
        -F float : the logarithmic fanout delay parameter [default = 0.00]
        -S float : the slew parameter used to generate the library [default = 0.00]
        -G float : the gain parameter used to generate the library [default = 250.00]
        -M num   : skip gate classes whose size is less than this [default = 0]
        -a       : toggles area-only mapping [default = no]
        -r       : toggles area recovery [default = yes]
        -s       : toggles sweep after mapping [default = no]
        -p       : optimizes power by minimizing switching [default = no]
        -f       : do not use large gates to map high-fanout nodes [default = no]
        -u       : use standard-cell profile [default = no]
        -o       : toggles using buffers to decouple combinational outputs [default = no]
        -v       : toggles verbose output [default = no]
        -h       : print the command usage
** cmd error: aborting 'source ./testsplit.script'