shell: reformatted, fixed inspections, typos

[pasabanov]

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• I have updated the documentation (in doc/) to reflect the changes made (if applicable)

#1986 #2006 #2113

Describe changes:

Reformatted shell scripts according to ShellCheck.

I. Most common changes:

1. https://github.com/koalaman/shellcheck/wiki/SC2086
   $var → "$var"
   Note: this isn't always necessary and I've been careful not to substitute where it wasn't necessary in meaning.
2. https://github.com/koalaman/shellcheck/wiki/SC2006
   `command` → $(command)
3. https://github.com/koalaman/shellcheck/wiki/SC2004
   $(( $a + $b )) → $(( a + b ))
4. https://github.com/koalaman/shellcheck/wiki/SC2164
   cd "$dir" → cd "$dir" || exit 1
5. https://github.com/koalaman/shellcheck/wiki/SC2166
   [ check1 -o check2 ] → [ check1 ] || [ check2 ]
6. https://github.com/koalaman/shellcheck/wiki/SC2002
   cat "${file}" | wc -c → < "${file}" wc -c
   Note: this looks a bit uglier but works faster.

II. Some special changes:

1. In file utils/common.sh:
   https://github.com/koalaman/shellcheck/wiki/SC2112
   This script is interpreted by sh, not by bash, but uses the keyword function.
   So I replaced #!/usr/bin/env sh to #!/usr/bin/env bash.
2. After that I thought of replacing all shebangs to #!/usr/bin/env bash for consistency and cross-platform compatibility, especially since most of the files already use bash.
3. But in cases when it was #!/bin/sh -e or #!/bin/bash -eu another problem appears:
   https://github.com/koalaman/shellcheck/wiki/SC2096
   So I decided to make all shebangs look uniform:

   #!/usr/bin/env bash
   set -e (or set -eu) (if needed)
   

4. In file tests/ossfuzz.sh:
   https://github.com/koalaman/shellcheck/wiki/SC2162
   read i → read -r i
   Note: I think that there is no need in special treatment for backslashes, but I could be wrong.
5. In file tests/do.sh.in:
   https://github.com/koalaman/shellcheck/wiki/SC2035
   ls *.*cap* → ls -- *.*cap*
6. In file utils/verify_dist_tarball.sh:
   https://github.com/koalaman/shellcheck/wiki/SC2268
   [ "x${TARBALL}" = x ] → [ -z "${TARBALL}" ]
7. In file utils/check_symbols.sh:
   https://github.com/koalaman/shellcheck/wiki/SC2221
   '[ndpi_utils.o]'|'[ndpi_memory.o]'|'[roaring.o]') → '[ndpi_utils.o]'|'[ndpi_memory.o]')
8. In file autogen.sh:
   https://github.com/koalaman/shellcheck/wiki/SC2145
   echo "./configure $@" → echo "./configure $*"
   https://github.com/koalaman/shellcheck/wiki/SC2068
   ./configure $@ → ./configure "$@"

III. LIST6_MERGED and LIST_MERGED6
There were typos with this variables in files utils/aws_ip_addresses_download.sh, utils/aws_ip_addresses_download.sh and utils/microsoft_ip_addresses_download.sh where variable LIST6_MERGED was defined, but LIST_MERGED6 was removed by rm.
I changed all LIST_MERGED6 to LIST6_MERGED.

Not all changes are absolutely necessary, but some may save you from future bugs.

[utoni]

LGTM

[IvanNardi]

Particularly appreciated the detailed commit message

[pasabanov]

Particularly appreciated the detailed commit message

You mean pull request message?

The commit message is not that detailed.

[IvanNardi]

Particularly appreciated the detailed commit message

You mean pull request message?

The commit message is not that detailed.

Yes, PR message, sorry. I copied it in the commit message