libibverbs: Support both OFED verbs and ibverbs

libibverbs: Support both OFED verbs and ibverbs

From: Sean Hefty <sean.hefty@intel.com>

This patch allows libibverbs to support both libibverbs API that
shipped with OFED 1.5 and the upstream libibverbs API.  This
supports existing apps that are compiled against the upstream
libibverbs (ibverbs).  And in ideal cases, an application
coded to the OFED version of libibverbs (ofverbs) would only
need to be recompiled with 'CFLAGS=-DOFED_VERBS' given as a
configuration option.

Support for OFED verbs is done using macros that convert the OFED
APIs to ibverbs APIs.  In most cases, simple data casts are all
that are necessary, with XRC support being the primary exception.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>