Found the following:
* Potential stack explosions with alloca() usage on potentially large
strings
* Memory leaks in WriteEngineServer
* Stack usage out of scope in dataconvert
* A typo in an 'if' statement in dataconvert
Add more comments.
Changed return value for HDFS'es fallocate.
Removed unnecessary code in ColumnBufferCompressed::writeToFile
Replaced Nulls with Empties in variable names.