Preallocate memory when SecStreamInBodyInspection is on

[allanbomsft]

This is an improved fix for #1366 .

• Preallocate memory when SecStreamInBodyInspection is on. On my dev box this gave 20x speed improvement for 10mb upload (and even more for larger files).
• Simplified the structure of modsecurity_request_body_to_stream
• Removed null termination for the stream_input_data buffer, as I did not see a reason for having this. The buffer is not a string. A request body can contain binary data.
• Fixed a typo in build_yajl.bat
• Added a check of the return value of modsecurity_request_body_to_stream

Thanks!

[zimmerle]

Fixed a typo in build_yajl.bat -> merged! thanks!

Looking the other stuff.

[zimmerle]

Indeed, that seems to be a good optimization. However, it may not be an optimization for certain users where the uploads are very small, therefore making it an optional compilation flag.

Thanks @allanbomsft