eal: add missing C++ guards

eal: add missing C++ guards

Some public header files were missing 'extern "C"' C++ guards,
and couldn't be used by C++ applications. Add the missing guards.

Fixes: af75078fece3 ("first public release")
Fixes: 7f3aa0863903 ("eal: introduce bit operations API")
Fixes: 166a743c53fa ("compat: add infrastructure to support symbol versioning")
Fixes: 8f40ee0734c8 ("eal/x86: get hypervisor name")
Fixes: 75583b0d1efd ("eal: add keep alive monitoring")
Fixes: 88701645c98c ("eal: move interrupt type out of igb_uio")
Fixes: f04519d8092e ("lib: add missing include dependencies")
Fixes: f58880682c81 ("trace: implement register API")
Fixes: 428eb983f5f7 ("eal: add OS specific header file")
Cc: stable@dpdk.org
Signed-off-by: Brian Dooley <brian.dooley@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>