Fix compilation with GCC 10+

[chris-durand]

The current release v2.51.1 fails to compile with more recent GCC versions starting from 10. The header file src/libusb/libusb.h uses a #if 0 preprocessor directive to specify a comment block. That comment contains the Unicode character ´ (Left Single Quotation Mark, U+2018) which is rejected by the compiler.

If gcc versions greater than 9 are used, compilation fails. Here the try to compile librealsense on Ubuntu with gcc 11 (g++ --version: Ubuntu 11.2.0-19ubuntu1):

[ 66%] Building CXX object CMakeFiles/realsense2.dir/src/libusb/context-libusb.cpp.o
In file included from /home/robot/librealsense/src/libusb/context-libusb.h:10,
                 from /home/robot/librealsense/src/libusb/context-libusb.cpp:4:
/home/robot/librealsense/src/libusb/libusb.h:10:82: error: extended character ‘ is not valid in an identifier

This fix replaces the rejected Unicode character with a plain ASCII single quote '.

[Ar-Ray-code]

@chris-durand
I encountered the same error in a build on Raspbian-bullseye and solved it with your suggestion.
Thanks.

[Nir-Az]

Hi @chris-durand,
Nice catch!
We'll take it 🥇

[Nir-Az]

Looks good!