[CMake] Add UTF8PROC_NO_INSTALL option

[past-due]

In some cases (such as using the library via add_subdirectory in CMake), it may be desirable to disable installation.

[stevengj]

Thanks, seems reasonable, though it would be better if cmake provided a cleaner way to do this from the parent (as is discussed in various places online, e.g. https://stackoverflow.com/questions/35344132/cpack-exclude-install-commands-from-subdirectory-googletest-directory/35345933, glfw/glfw#30, ...)

I modifed the PR so that it is UTF8PROC_INSTALL=No, however.