Replace use of the deprecated exec_program with execute_process

See merge request !16

Change minimum CMake version to 3.5

See merge request !15

CMake is no longer supporting versions earlier than that. We are
going to follow along with that.

Create target properties to add command line options

Closes #10

See merge request !14

Also reformat to use the \url command.

Be less clever about README links

See merge request !12

Previously, the download links in the README file contained the
full URL to the latest version of the CMake and PDF. The problem
is that this URL is fragile. It always points to the top copy
(as opposed to the current commit if looking at a particular
verion). Plus the URL could change with updates to GitLab or
other configuration changes.

Just link to the file and let GitLab provide the right page.
This is a bit less nice as you get the GitLab source view, but
you still get a download link right on it. I'm sure users can
figure it out.

Handle condition with user-set comment character

See merge request !11

The release-version.sh script creates an automatic version tag
description. At the bottom it puts comments for further
instructions. These comments used the '#' comment character.
However, this character can be changed by the git configuration.
So, instead read the git configuration and use the appropriate
comment character no matter what.

Prepare to release version 2.7.2

See merge request !10

Add CONFIGURE_DEPENDS option when globbing files

Closes #9

See merge request !9

This allows better detection when files in a directory change.
This only happens for CMake 3.12 or better.

Update minimum CMake to 2.8.12

See merge request !8

The latest version of CMake gives a deprecation warning if you
set the minimum required CMake to earlier than that.

Technically, the minimum version of CMake is not defined by
UseLATEX.cmake itself, but it is defined in all the test and
in an the main documentation build, which itself is used as
an example.

Update version to 2.7.1

See merge request !7

Ignore warning about font shape having incorrect series

See merge request !6

It is not uncommon to get a LaTeX warning like the following:

LaTeX Warning: Font shape declaration has incorrect series value `mc'.

The warning appears to be harmless. (I saw that on the internet
so it must be true, right?) It is also not trivial to get rid of
since some combination of packages or distributions can cause it.

Fix error conditions with file spaces

Closes #7

See merge request !5

On error condition UseLATEX.cmake reads in some generated LaTeX
files. If those files have spaces (and LaTeX decides to actually
work with files with spaces) properly handle the generated files
on an error condition.

Add license

Closes #6

See merge request !3

Add a license file to the top-level directory.

The previous version of release-version.sh was dropping the first
line of the release notes. This change adds that first line to
the release notes.

INPUT_DIRECTORIES option

See merge request !2