eina mmap safety - only map zeropages if it's an eina file that sigbuses

eina mmap safety - only map zeropages if it's an eina file that sigbuses

restrict mapping /dev/zero to only eina files having a sigbus
reported. the mmap was before all our file access used eina_file i
think thus the raw mmap of it. now walk all eina files and find the
candidate and only then if it exists flag is as having a faulty i/o
backing and map the zerto pages then return, otherwise call abort.
more restricted mapping and perhaps a fix for not trapping non-efl
issues.

@fix