A suburban Boston prosecutor said he will seek to charge hundreds of anti-abortion demonstrators with a violation of the state's Civil Rights Act instead of merely with disorderly conduct. Norfolk County Dist. Atty. William Delahunt said the new charges would represent the first time in Massachusetts, and probably in the nation, that interfering with a woman's right to an abortion would be interpreted as a civil rights violation. He said he would drop disorderly conduct charges against about 360 people today and file the civil rights charges, which would have to be considered later by a grand jury. Civil rights violations can bring a jail term of up to a year and a fine of up to $1,000.