change cstdlib abs to cmath abs(float). in mingw 4.9.1 abs(in castlib…

[dushibaiyu]

change cstdlib abs to cmath abs. in mingw 4.9.1 abs(in castlib) is erro.
funtion abs in cstdlib is : http://www.cplusplus.com/reference/cstdlib/abs/
in cmath is : http://www.cplusplus.com/reference/cmath/abs/

[Benjamin-Dobell]

Could you please elaborate on the reason for the change?

Also, please don't leave commented-out code - just delete the line(s).

[dushibaiyu]

in file /core/src/zxing/pdf417/detector/LinesSampler.cpp
in about line 708:
float denom = dxa * dyb - dya * dxb;
if(abs(denom) < 1e-12) // Lines don't intersect (replaces "denom == 0")
In default it use abs in cstdlib,. funtion abs in cstdlib can't handle abs(float). So , in my build (win7,mingw 4.9.1), there is a erro. I include cmath , replace abs funtion the used to abs(float) in cmath. it is ok.
the action used funtion abs in cstdlib is same to funtion abs in cmath. they are |x|。

Sorry， my english is bad.

[Benjamin-Dobell]

Alright, seems reasonable. Merging...