dlopen: only FI_WARN if user specified $FI_EXTDIR

Specifically: don't emit a warning message if the default/compiled-in
extdir does not exist.

Also remove a debugging FI_WARN for when we detect static linking.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
usnic: check for <infiniband/verbs.h>

The usnic provider uses <infiniband/verbs.h> to get some of the verbs
kernel ABI enums, so check for it in the usnic configury.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
build: fix build for enable direct

Only one provider can be built in direct mode, so we
keep a count. Also, additional headers need to be
installed.

Include a check to see if the requested provider supports
direct mode, if the user requests to build the provider
as direct.

Quote message in AC_MSG_WARN in square brackets.

Fixes #194

Signed-off-by: Sayantan Sur <sayantan.sur@intel.com>
Merge pull request #200 from sayantansur/fi-direct

build: fix build for enable direct
Merge pull request #195 from jsquyres/topic/dlopen-fixes

dlopen: sanity check the DL directory
Merge pull request #204 from jsquyres/pr/usnic-infiniband-verbsh-check

usnic: check for <infiniband/verbs.h>
Merge branch 'master' into usdf
flesh out EQ