Start a program in a subprocess. Return the process object for it.
NAME is name for process. It is modified if necessary to make it unique.
BUFFER is the buffer (or buffer name) to associate with the process.
Process output (both standard output and standard error streams) goes
at end of BUFFER, unless you specify an output stream or filter
function to handle the output. BUFFER may also be nil, meaning that
this process is not associated with any buffer.
PROGRAM is the program file name. It is searched for in `exec-path'
(which see). If nil, just associate a pty with the buffer. Remaining
arguments are strings to give program as arguments.
If you want to separate standard output from standard error, invoke
the command through a shell and redirect one of them using the shell
syntax.
(fn NAME BUFFER PROGRAM &rest PROGRAM-ARGS)