Merge pull request #141 from YaroslavLitvinov/dev

Dev
fix libtar symbols

Provided unique symbols instead of "common" names, like
"print_header" or "buffer". These symbols frequently clashed with
symbols from other software. Because libtar is a part of ZRT it is
linked to each and every binary.
This fixed rudimentary symbols without prefix for libtar
Fixed bug caused to abort at exit

Call of postmain handler added to fix abnormal termination of zrt
program if /dev/alloc_report channel was present and also exporting
files feature was enabled in nvram file; Errors were occured while
collecting allocation info, particularly during backtrace call
which is not designed to be called out of bounds of main function.