* Update libssh2 package to 1.8.1

* Add pre-built binaries for libssh2

* Update binaries for libssh2 in install.sh

* Update php7 to 7.1.27

* Update php7 to 7.3.3

* Update php7 to 7.2.16

* Update php packages

Uses regex on File.basename(). Using File.extname() on some
files (ie, archive.tar.gz) can lead to unexpected behavior.

Add pre-built binaries

This was mentioned in the FAQ, however, gtk2 is not installed.

Add some best practices to harden dev mode
Source: https://dev.to/isr/comment/6a03

Add pre-built binaries

Add pre-built binaries

Change dependency from python27 to six

Convert file operations to use FileUtils

Add pre-built binaries

Convert all file operations to use FileUtils

Check for free disk space

Add postinstall message about complete removal

Uncomment free disk space check

Add LIBC_VERSION constant

Fix uninitialized variable usage

Add pre-built binaries

Add pre-built binaries

Make sure x86_64 libraries are installed in #{CREW_PREFIX}/lib64

Update x86_64 pre-built binary

Add pre-built binaries

Add pre-built binaries

Fix wrong i686 binary url in gtk2 package

Change binary element positioning to be consistent with other packages

Fixes #3126?

* Add kcov package

* Fixing dependency for kcov package

* Check package dependencies more efficiently

Keep track of the names of dependencies that have already been checked
in the expand_dependencies/push_dependencies loop. A quick and dirty way
to break out of dependency cycles and speed up the dependency resolution
step in general.

* Simplify the logic of dependency checking in expand_dependencies

Accomplishes the same goal without needing to explicitly keep a list of
previously-checked dependencies.