Added HangDetectorPropertyTask to the PropertyTask tests.

I want to add some tests that currently fail to detect a circular
reference, but running these tests (obviously) causes PHPUnit to
hang which is very unpleasant.

HangDetectorPropertyTask extends PropertyTask and uses a custom
HangDetectorProperties (extends Properties) that counts the number
of accesses. More than 100 is interpreted as an undetected circular
reference. Don't use big property sets when testing...
Changed test3 to testCircularReferenceDetection and added data provider.
Add two new PropertyTask tests where circular definition detection fails.

Below, A->B means resolves to B in some way, like A=xx${B}yy

Currently a chain like A->B->A will be detected in the
resolveAllProperties() function since we check each new property in the
chain against the property were trying to resolve.

This fails if we start to resolve A but the circular chain doesn't
involve A:
A->B->C->B->C->B....

These two tests reflect that.
For consistence, it's circular "Definition", not "Reference".
Fix for the tests testCircularDefinition1 and testCircularDefinition2.

In resolveAllProperties() we remember which properties from $props have
been used to resolve the current property. If the same property appears
twice, we have a circular property definition.

This will detect chains like A resolves to B resolves to C resolves to B...
Forgot to add file...
update url for d51PearPkgTask
Merge pull request #265 from BigMichi1/patch-1

update url for d51PearPkgTask
fix docblocks of pearpackagefileset
add links to most nested tag lists
Merge pull request #266 from cweiske/links

add links to most nested tag lists
Fixed possible race condition in MkdirTask

See http://stackoverflow.com/questions/9290591/mkdir-in-ant-fails-how-can-i-handle-this-error
Merge pull request #267 from kostiklv/patch-1

Fixed possible race condition in MkdirTask
Disable webhelp generation
Update output targets
enable phar writing when running phing

By default, PHP applications may not modify phar archives
because php.ini defines phar.readonly=1.

The phing wrapper script now sets phar.readonly=0 via
a commandline parameter to PHP, so that <pharpackage>
can properly write .phar files.
Fix #1085: Conditions section (5.8) does not correctly link to mentioned tasks

Also fixes some related links that were broken.
Fix #964: includePathTask: talk about appending/prepending
Merge pull request #270 from cweiske/fix-964

Fixes #964: includePathTask: talk about appending/prepending
Merge pull request #269 from cweiske/fix-1085

Fixes #1085: Conditions section (5.8) does not correctly link to mentioned...