Feature request: PROMPT_COMMANDS array variable

[Daniel Colascione]

Right now, PROMPT_COMMAND gives a shell command to run before displaying
the prompt. It's common these days to include in one's bash configuration
numerous packages from different sources that *all* want to run code at
PROMPT_COMMAND time. Can we add a new PROMPT_COMMANDS array variable that
stores a list of shell commands to execute? With a PROMPT_COMMANDS
variable, different packages can independently add their hooks without
stepping on each other.