more searchpath-related changes

document isum

stupid bugs

rename scheduler to have a more distinctive name, so stack traces can end there

avoid saying unsigned long, for unix port

add undocumented Abort builtin

do not clobber register names

add stack

document -q

document core and stack

sort cores; print stack as command

changes mainly for threading support

less verbose

change to use attach functions. $a means switch thread in core dumps. (maybe that should be $A now?).

Working on better handling of multithreading in general and core dumps in particular. See notes: new types: register is something that when dereferenced gives you the registers. the Ureg is no longer mapped at 0. refconst is something that gives a constant when dereferenced. new builtin register("AX") creates register values new builtin refconst(0x123) creates refconst values new builtin var("foo") is equivalent to the variable foo (it returns foo but can also be used as the lhs of an assignment). new acid function getregs() returns a list of the current values of registers. new acid function setregs() sets the current registers to those values. note that getregs and setregs operate on register locations, not the register values themselves. new acid function resetregs() sets registers to register("AX"), etc. new acid function clearregs() sets all registers to constant -1. the default register settings are as in resetregs(), not small numbers. new acid variables coretext, pids, systype, corefile, cmdline. new behavior: local variable lookup, stk, etc., use the acid values of registers (*PC, *SP, and so on), so the thread support code can change the context completely. unary + is applicable to more data types and prints more often.