eal: make OS shims internal

eal: make OS shims internal

DPDK code often relies on functions and macros that are not standard C,
but are found on all platforms, even if by slightly different names.
Windows <rte_os.h> provided macros or inline definitions for such symbols.
However, when placed in public header, these symbols were unnecessarily
exposed, breaking consumer POSIX compatibility code.

Move most of the shims to <rte_os_shim.h>, a header to be used instead
of <rte_os.h> by internal code. Include it in libraries and PMDs that
previously imported shims from <rte_os.h>. Directly replace shims that
were only used inside EAL:
* index -> strchr, rindex -> strrchr
* sleep -> rte_delay_us_sleep
* strerror_r -> strerror_s

Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Ranjit Menon <ranjit.menon@intel.com>