Build/DEB dependencies: libegl1-mesa --> libegl1

Since Ubuntu 18.04, the EGL libraries have been distributed in a package
named libegl1, and libegl1-mesa has been a transitional dummy package
that points to libegl1.  In Ubuntu 23.10, the transitional dummy package
was removed, which caused a dependency error when attempting to install
an official VirtualGL package.  Ubuntu 16.04 LTS was the last Ubuntu
release supported by VirtualGL that didn't have a libegl1 package, and
it has been EOL since 2021.  (Ubuntu 18.04 LTS is now EOL as well, as of
earlier this year.)  Thus, we can safely change our package dependency
from libegl1-mesa to libegl1.

Fixes #242

cmakescripts/BuildPackages.cmake

@@ -80,7 +80,7 @@ add_custom_target(srpm pkgscripts/makesrpm
 
 set(EGLDEPENDS "")
 if(VGL_EGLBACKEND)
-	set(EGLDEPENDS ", libegl1-mesa:${DEBARCH}")
+	set(EGLDEPENDS ", libegl1:${DEBARCH}")
 endif()
 configure_file(release/makedpkg.in pkgscripts/makedpkg)
 configure_file(release/deb-control.in pkgscripts/deb-control)