Fixed bug local block parsing data size, check for local size incomplete

[0xCCF4]

In the ZIP Format Specification (version 6.3.10) it is defined that for a local file header (section 4.3.7) flag bit 3 (section 4.4.4) may be set to indicate that the data size can be found in the data descriptor. A supporting implementation must in that case set crc32, compressed and uncompressed size to zero.

From the specification:

Bit 3: If this bit is set, the fields crc-32, compressed 
               size and uncompressed size are set to zero in the 
               local header.  The correct values are put in the 
               data descriptor immediately following the compressed
               data.  (Note: PKZIP version 2.04g for DOS only 
               recognizes this bit for method 8 compression, newer 
               versions of PKZIP recognize this bit for any 
               compression method.)

We can therefore assume that if C/U size or crc32 is not set to zero in the local file header, the given size is valid and can be used to determine the content size

I observed that some zip compression utils in fact include the size in the local file header while still setting bit 3.

My contribution:

• change the check if a local size is contained in the local entry parser
• add tests to test this feature

[Pr0methean]

Looks great, but could you please fix the failing style checks and unit tests?

[0xCCF4]

I've done some more testing and it seems that my initial claim in #196 (comment) is not entirely true. My compressing program is not specification compliant and inserts the uncompressed size in the local file header while setting the compressed file size to zero. Which does not help with the size detection. I therefore close the PR.