Hi Rong,

    Please review this code. This code allows the function reordering
plugin to separate hot and cold code into different ELF segments.
This would allow optimizations like mapping the hot code alone to huge
pages.

    With this patch, by default, the plugin maps .text.unlikely
sections into a separate ELF segment.  This can be turned off with
plugin option "--segment=none".

    The include/plugin-api.h changes are a backport from trunk.

Thanks,
-Sri.