round seconds in command timing information if precision is >= 0; fix for readline...

round seconds in command timing information if precision is >= 0; fix for readline word boundaries when quoted command substitutions appear; remove nameref attribute when converting nameref variable into an array; change how help strings are written to builtins.c; change read builtin to update unwind-protect if the input string is reallocated; fix crash when an expansion on the rhs of an assignment statement unsets the variable on the lhs