update copyright dates

gas/app.c

gas/as.c

gas/atof-generic.c

gas/bignum-copy.c

gas/bignum.h

gas/bit_fix.h

gas/cgen.h

gas/cond.c

gas/depend.c

gas/doc/all.texi

gas/doc/as.texinfo

gas/doc/c-alpha.texi

gas/doc/c-arm.texi

gas/doc/c-cris.texi

gas/doc/c-d10v.texi

gas/doc/c-h8300.texi

gas/doc/c-h8500.texi

gas/doc/c-i370.texi

gas/doc/c-i386.texi

gas/doc/c-i960.texi