Fixed CUSPICE compilation under NVCC versions prior than 6.0. CUSPICE will be compiled for every architectures supported by NVCC
Fixed configure.ac file to let the user specify his custom CFLAGS
Moved Truncation Error Calculation into GPU for CUSPICE
Merge branch 'CUSPICE' of ssh://git.code.sf.net/p/ngspice/ngspice into CUSPICE

Conflicts:
	src/spicelib/analysis/cktsetup.c