blob: removed experimental EBLOB_DROP_PAGE_CACHE flag

For testing purposes page cache helpers should be used, e.g. vmtouch:
    https://github.com/SaveTheRbtz/vmtouch
data-sort: fixed memory leak in datasort_mkdtemp()

Found with: Coverity Prevent (tm)
mobjects: check return code of rename

Found with: Coverity Prevent (tm)
mobjects: simplified eblob_rename_blob
blob: check return code of malloc

Found with: Coverity Prevent (tm)
blob: improved error reporting