glx: fixup symbol name for get_extensions function
glxProbeDriver() concatenates __DRI_DRIVER_GET_EXTENSIONS with driver name to get symbol name for get_extension function. Unfortunately that doesn't work for drivers that have hyphen in their name, e.g. sun4i-drm -- get_extensions() for these uses underscore instead.
As result dlsym() doesn't find get_extension() function and AIGLX initialization fails resulting in following message in Xorg.0.log:
(EE) AIGLX error: sun4i-drm does not export required DRI extension
Replace all non-alpha-numeric characters with underscore to fix the issue.
Signed-off-by: Vasily Khoruzhick anarsoul@gmail.com