buildroot

libwebsockets: bump to v1.7.3

 - Drop
   0001-cmake-disable-shared-library-build-when-BUILD_SHARED.patch,
   since CMakeLists has been reworked. Static/shared build can now be
   configured via configuration options.

 - Add support for optional libev and libuv.

 - Use the github macro for download.

 - Update hash.

Signed-off-by: Sagaert Johan <sagaert.johan@proximus.be>
[Thomas: tweak the commit log a bit.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>