Upon special request by Andy Clement, I included 'lib' as a child module
in the parent POM again, making several modules which refer to
downloaded library files dependent the 'lib' module. I am not sure I
caught all of them, but I hope so.

Now after cloning the project and configuring the token for reading from
GitHub Packages (sorry!), you can just run a Maven build for the main
project and no longer need to fail the first build, read the Maven
Enforcer message and run 'cd lib && mvn compile' as a first step. This
convenience comes at the price of a more complex POM and two new
profiles:

  - Profile 'provision-libs' is auto-activated by the absence of a
    marker file, kicking off the library provisioning process and
    creating same marker file at the end, if successful. Therefore,
    during subsequent builds libraries will not be re-provisioned,
    because the marker file exists and Maven skips all download and
    (un)zip steps, which saves build time and bandwidth. Otherwise
    offline builds would not work either.

  - Profile 'clean-libs' needs to be activated manually, because by
    default 'mvn clean' will not erase provisioned libraries. In most
    cases, even after a clean a developer does not want to re-provision
    all libraries if they have not changed (e.g. new JDT Core build).
    But if you do wish too erase the libraries and the marker file, just
    call 'cd lib && mvn -P clean-libs clean'.

Please note: The Maven Enforcer build step, which additionally checks
for existence of other files, still exists and was moved from the parent
POM to 'libs'. No matter if provisioning was just done or skipped
because the main marker file exists, a quick heuristic check for that
list of files is done during each build, failing the build with a
comprehensive message if an inconsistency was found. The error message
says which files are missing and tells the user:

  "There is an inconsistency in module subdirectory 'lib'. Please run
  'mvn --projects lib -P clean-libs clean compile'. This should take
  care of cleaning and freshly downloading all necessary libraries to
  that directory, where some tests expect them to be."

This should cover the topic.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

The new string AjcTestCase.CLASSPATH_ASM_RENAMED dynamically determines
the 'asm-renamed' location from the classpath, system property
'java.class.path'.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

Actually, only fop:fop:0.20.5 and batik:batik-1.5-fop:0.20-5 are really
used in addition to lib/saxon/saxon.jar (saxon:saxon:6.5.3). So the rest
does not need to be replaced and can just be wiped.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

It was kind of difficult to identify and find the vintage versions used
in AspectJ in download archives, but finally I managed to. Docs
generation looks good visually, tests to be run on GitHub CI.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

Because 'cd lib && mvn compile' can now download and (un)zip many
previously SCM-committed third-party dependencies, the following 'lib'
subdirectories have been deleted:
 - ant
 - asm
 - commons
 - jarjar
 - junit
 - regexp
 - saxon
This one is new (but not stored in SCM):
 - jdtcore-aj

For each of them, there now is a .gitignore entry, so as to prevent
developers from accidentally committing the downloaded binaries again.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

There are two files:
  - docs/developer/ram-disk/maven.config
  - docs/developer/ram-disk/settings-ramdisk.xml

The latter contains info about how to set up a development environment
inside a RAM disk. Both files are to be copied to the project's '.mvn'
folder in the root directory and adjusted according to the description.

Just in case, .gitignore ignores the files if they exist in '.mvn', so
they are not being staged and committed accidentally.

An additional screenshot shows how to configure the Windows Recycle Bin
to immediately delete files in order too save space on the RAM disk.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>