travis: Update build environments

Add Ubuntu's Focal distribution to get the latest Linux toolchain.

Add Xcode 12.2 to get the latest MacOS toolchain.

Remove Xcode 7.3 as it is now obsolete and will not successfully build.

Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index 47ce5aa..35326e3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,6 +6,12 @@
 matrix:
     include:
         - os: linux
+          dist: focal
+          compiler: clang
+        - os: linux
+          dist: focal
+          compiler: gcc
+        - os: linux
           dist: bionic
           compiler: clang
         - os: linux
@@ -18,14 +24,14 @@
           dist: xenial
           compiler: gcc
         - os: osx
+          osx_image: xcode12.2
+          compiler: clang
+        - os: osx
           osx_image: xcode11.3
           compiler: clang
         - os: osx
           osx_image: xcode9.4
           compiler: clang
-        - os: osx
-          osx_image: xcode7.3
-          compiler: clang
 
 addons:
     apt:

libusb/version_nano.h

diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index 4e73d5c..9c3a26e 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11571
+#define LIBUSB_NANO 11572