Handle field separations with lambdas, similarly to record separation. The idea is that we replace the rec-to-f method, which contains a cond statement checking the variables for which field separation discipline applies, with a lambda which is updated whenever any of those ariables change. * awk.tl (awk-state): New instance slot, rec-to-f. (awk-state :postinit): Call new upd-rec-to-f method so that rec-to-f is populated with the default field separating lambda. (awk-state rec-to-f): Method removed. (awk-state upd-rec-to-f): New method, based on rec-to-f. This doesn't perform the field separation, but returns a lambda which will perform it. (awk-state loop): We must call upd-rec-to-f whenever we change par-mode, because it influences field separation. (awk-mac-let): Replace the symbol macros fs, ft, fw and kfs with new implementations that use the reactive slot mechanism provided by rslot. Whenever the awk macro assigns any of these, the upd-rec-to-f method will be called. * tests/015/awk-basic.tl: New file. These basic tests of field separation pass before and after this change. * tests/common.tl (otest, motest): New macros.