maint: Use new C++ archetype in more files. Place input validation first in files. Move declaration of retval down in function to be closer to point of usage. Eliminate else clause after if () error. Use "return ovl()" where it makes sense. * __dispatch__.cc, __dsearchn__.cc, __ichol__.cc, __lin_interpn__.cc, balance.cc, betainc.cc, bitfcns.cc, bsxfun.cc, cellfun.cc, colloc.cc, conv2.cc, daspk.cc, dasrt.cc, dassl.cc, data.cc, debug.cc, dirfns.cc, dlmread.cc, dot.cc, eig.cc, error.cc, fft.cc, fft2.cc, fftn.cc, file-io.cc, ov-type-conv.h: Use new C++ archetype in more files.