md5 hashed zero byte lock files from system log flood hook

[rengaw83]

The GeneralUtility-Hook creates a lot md5 hashed of zero byte files in the typo3temp/rn_base directory. A deletion of these files has not been provided yet.

• don't use a md5 as name. Otherwise nobody knows where the file is from.
  better user MktoolsLogFlood_[EXTKEY][SEVERITY]_[MSG-MD5] or something similar.
• there has to be a process to delete the lock files after lifetime expires. This can be done in the constructor/destructor and should be performend only once per php process.