Search for correct libusb in testing.

There may be many libusb libraries on a system, and we need to iterate until we
find the correct one.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

diff -Nuar --exclude .libs --exclude '*.o' --exclude core nut-2.7.1.orig/tools/nut-scanner/scan_usb.c nut-2.7.1/tools/nut-scanner/scan_usb.c
--- nut-2.7.1.orig/tools/nut-scanner/scan_usb.c	2014-01-04 18:38:22.496816444 -0800
+++ nut-2.7.1/tools/nut-scanner/scan_usb.c	2014-01-04 19:05:04.598647935 -0800
@@ -28,7 +28,7 @@
 #include <ltdl.h>
 
 /* dynamic link library stuff */
-static char * libname = "libusb";
+static char * libname = "libusb-0.1";
 static lt_dlhandle dl_handle = NULL;
 static const char *dl_error = NULL;
 static int (*nut_usb_close)(usb_dev_handle *dev);
@@ -41,6 +41,8 @@
 static usb_dev_handle * (*nut_usb_open)(struct usb_device *dev);
 static int (*nut_usb_find_devices)(void);
 
+int nutscan_test_usb_library(const char*,void*);
+
 /* return 0 on error */
 int nutscan_load_usb_library()
 {
@@ -58,6 +60,22 @@
 		return 0;
 	}
 
+	int ret = lt_dlforeachfile(NULL, nutscan_test_usb_library, libname);
+	if(ret == 0) {
+		dl_handle = (void *)1;
+		lt_dlexit();
+	}
+
+	return ret;
+}
+
+int nutscan_test_usb_library(const char *filename, void* data) {
+		char prefix[64];
+		char *libname  = (char*) data;
+		sprintf(prefix, "/%s", libname);
+		if(strstr(filename, prefix) == NULL)
+			return 0;
+
-        dl_handle = lt_dlopenext(libname);
+        dl_handle = lt_dlopenext(filename);
         if (!dl_handle) {
                 dl_error = lt_dlerror();
                 goto err;
@@ -100,16 +118,15 @@
                 goto err;
         }
 
         *(void **)(&nut_usb_find_devices) = lt_dlsym(dl_handle,"usb_find_devices");
         if ((dl_error = lt_dlerror()) != NULL)  {
                 goto err;
         }
 
+        fprintf(stderr, "Loaded USB library (%s from %s) : USB search enabled.\n", libname, filename);
         return 1;
 err:
-        fprintf(stderr, "Cannot load USB library (%s) : %s. USB search disabled.\n", libname, dl_error);
-        dl_handle = (void *)1;
-	lt_dlexit();
+        fprintf(stderr, "Cannot load USB library (%s from %s) : %s. USB search disabled.\n", libname, filename, dl_error);
         return 0;
 }
 /* end of dynamic link library stuff */