Make PSR0Fixer compatible with abstract class

It assumed "class|interface|trait" to be at the beginning of the line, though
classes can have the "abstract" keyword preceed the "class" keyword.
Instead of space, allow any whitespace between 'abstract' and 'class' keywords
merged branch matthiasmullie/master (PR #196)

This PR was merged into the master branch.

Discussion
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Make PSR0Fixer compatible with abstract class

It assumed "class|interface|trait" to be at the beginning of the line, though
classes can have the "abstract" keyword preceed the "class" keyword.

Commits
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2bacc31 Instead of space, allow any whitespace between 'abstract' and 'class' keywords
c07be99 Make PSR0Fixer compatible with abstract class