(1) disable documentation for .lsym at sac's request

(1) disable documentation for .lsym at sac's request
(2) structural changes triggered thereby
(3) verify m4 and makeinfo run correctly on all versions of the doc
    represented in the Makefile and m4 config definition files

as.texinfo: disabled .lsym
            exploit makeinfo node defaulting
            removed some conditional hair around nodes
            fixed some bad conditionals in a29k config
a29k.m4, i960.m4, sparc.m4, vax.m4: supply missing switch definitions
            (looks like these hadn't been tested for a while)
as-all.texinfo: mechanically derived from above