Support external libnanomsg better for --use_system_libnanomsg=true

nanomsg headers are installed in /usr/include/nanomsg.
However, depending on the version, nanomsg.pc provides either
-I/usr/include (useless) or -I/usr/include/nanomsg.

When using --use_system_libnanomsg=true, pass -DSYSTEM_NANOMSG=1
to the compiler.

Keep using the original includes when SYSTEM_NANOMSG is not defined.

Use #include <nanomsg/...> when SYSTEM_NANOMSG is defined because
it works regardless of the nanomsg version in the system.

Signed-off-by: Zoltán Böszörményi <[email protected]>

binding.gyp

@@ -24,6 +24,9 @@
           'libraries': [
             '<!@(pkg-config nanomsg --libs || echo "")'
           ],
+          'defines': [
+            'SYSTEM_NANOMSG=1',
+          ],
         }],
         ['OS=="mac" and use_system_libnanomsg=="true"', {
           'include_dirs+': [
@@ -32,6 +35,9 @@
           'libraries': [
             '<!@(pkg-config nanomsg --libs || echo "")'
           ],
+          'defines': [
+            'SYSTEM_NANOMSG=1',
+          ],
         }],
         ['OS=="mac" and asan=="true"', {
           'xcode_settings': {

src/node_nanomsg.cc

@@ -1,16 +1,43 @@
+#ifndef SYSTEM_NANOMSG
+
 #include "bus.h"
 #include "inproc.h"
 #include "ipc.h"
 #include "nn.h"
 #include "pair.h"
 #include "pipeline.h"
+
+#else
+
+#include "nanomsg/bus.h"
+#include "nanomsg/inproc.h"
+#include "nanomsg/ipc.h"
+#include "nanomsg/nn.h"
+#include "nanomsg/pair.h"
+#include "nanomsg/pipeline.h"
+
+#endif
+
 #include "poll_ctx.h"
+
+#ifndef SYSTEM_NANOMSG
+
 #include "pubsub.h"
 #include "reqrep.h"
 #include "survey.h"
 #include "tcp.h"
 #include "ws.h"
 
+#else
+
+#include "nanomsg/pubsub.h"
+#include "nanomsg/reqrep.h"
+#include "nanomsg/survey.h"
+#include "nanomsg/tcp.h"
+#include "nanomsg/ws.h"
+
+#endif
+
 NAN_METHOD(Socket) {
   int domain = Nan::To<int>(info[0]).FromJust();
   int protocol = Nan::To<int>(info[1]).FromJust();

src/poll_ctx.cc

@@ -1,4 +1,8 @@
+#ifndef SYSTEM_NANOMSG
 #include "nn.h"
+#else
+#include "nanomsg/nn.h"
+#endif
 #include "poll_ctx.h"
 
 void PollCtx::on_readable(uv_poll_t* req, int /* status */, int events) {