Moves error suppression to PHP functions for edd_readfile_chunked

No sense in sullying EDD functions with error suppression when it's PHP edge cases that require it, not EDD.  Also fixes a fair bit of standards kerfuffles as a result of copypasta.
Merge pull request #1995 from JustinSainton/patch-5

Moves error suppression to PHP functions for edd_readfile_chunked