Absorb spaces after 'stream' declarations

[GreyWyvern]

Type of pull request

• Bug fix (involves code and configuration changes)

About

When detecting the start of a stream, PdfParser currently expects the next character to be either a carriage-return (\r) or a newline (\n). If there is a space in between the stream and either the \r or the \n, it is not detected as a stream of data and is discarded.

Adjust the regexp in RawDataParser.php to absorb spaces after stream.

Resolves #641. Note that in the sample files provided by the original reporter of 641 there are remaining font decoding issues with the output that are outside the scope of this fix.

Checklist for code / configuration changes

• Please add at least one test case (unit test, system test, ...) to demonstrate that the change is working. If existing code was changed, your tests cover these code parts as well.
• Please run PHP-CS-Fixer before committing, to confirm with our coding styles. See https://github.com/smalot/pdfparser/blob/master/.php-cs-fixer.php for more information about our coding styles.
• In case you fix an existing issue, please do one of the following:
  • Write in this text something like fixes #1234 to outline that you are providing a fix for the issue #1234.