SERVER-14835 - fix fassert 16143 on PPC64 LE systems in LogFile::synchronousAppend()

new version, using ioctl(_fd, BLKBSZGET) and fixed predefined alignment for PPC64.
There's a set of #includes in the same file for non-Windows code around lines 160-165. You can move these #includes there and wrap linux/fs.h with __linux__.