Understand array variable declaration in read (fixes #679)

Add link to flymake-shellcheck under Emacs section

Expand "rhs"; this abbreviation seems needlessly obfuscating.

It used to only treat all trailing variables in read as varaible
declarings, but an array variable can be declared in other positions:

    read -a foo -r

foo is a declared variable, and multiple such variables can be declared.

I've recently created the flymake-shellcheck package for Emacs, which allows using ShellCheck with the built-in Flymake package.

Merge branch 'opqaque-interface' of https://github.com/ngzhian/shellcheck into ngzhian-opqaque-interface

Signed-off-by: NMartin Schwenke <martin@meltin.net>

Specifies the maximum severity of errors to handle.  For example,
specifying "-S warning" means that errors of severity "info" and
"style" are ignored.
Signed-off-by: NMartin Schwenke <martin@meltin.net>

Use regex to match special flags for printf

Fixes #1310

Fix #949 (failing on @ in function names)

'@' was previously mentioned in 5005dc0f as a
character needed to fix #909, but was not included
in the actual change at that time.

Fix false positive when indexing into array in cond

Fixes #1268

Add instructions to install linux binary