etc: add generic linux compatibility code

etc: add generic linux compatibility code

To support the porting of OFED code, such as the infiniband-diags, provide a
set of linux compatible include files and functions.

This adds a set of header files under inc/user/linux so #include statements
in code will find them.  In some cases, the header files are blank, but in
others, they contain mappings between the linux calls and equivalent windows
calls.

Where more complex functionality is needed, source files are added under
etc/user to provide it, similar to what was done for getopt.

These headers and source files are used to support the OFED infiniband-diags
in the WinOF build environment.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
git-svn-id: svn://openib.tc.cornell.edu/gen1/trunk@1993 ad392aa1-c5ef-ae45-8dd8-e69d62a5ef86