Fixed a bug in n_arg for double and binary mode, where -0.0 was  different form 0.0. Work in progress for the  interval mode.

Fixed "++" and "+-+" by replacing a*a with sqr(a). Better error message for square root of negative numbers.

mp.w: Fixed a buffer overflow. decContext.{c,h}, decNumber.{c,h}, decNumberLocal.h: Convert newline from CRLF to LF  (thanks to TANAKA Takuji).