Merge pull request #1 from brs332/master

Change pseries_defconfig to pseries; linux.mk adds _defconfig
Merge pull request #2 from brs332/master

Call bash rather than sh in hostboot.mk; fails on ubuntu 14.04
Merge pull request #3 from brs332/master

Sync with powerpc64_petitboot_defconfig
Merge pull request #4 from brs332/master

Add instructions for building on various platforms
Create separate filename variables for targeting.bin/.ecc