Doc and manual fixes related to processes

Doc and manual fixes related to processes

* doc/lispref/processes.texi (Processes, Subprocess Creation, Shell Arguments):
(Synchronous Processes): Copyedits.
(Subprocess Creation): Discourage modifying exec-path directly.
(Synchronous Processes): Update some example output.
(Process Information): Fix typo.
(Bindat Spec): Use Texinfo-recommended form of quote+punctuation.

* lisp/simple.el (process-file-side-effects): Doc fix.