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>

glx/glxdricommon.c

@@ -27,6 +27,7 @@
 #include <dix-config.h>
 #endif
 
+#include <ctype.h>
 #include <stdint.h>
 #include <errno.h>
 #include <dlfcn.h>
@@ -322,6 +323,15 @@ glxProbeDriver(const char *driverName,
                  __DRI_DRIVER_GET_EXTENSIONS, driverName) != -1) {
         const __DRIextension **(*get_extensions)(void);
 
+        for (i = 0; i < strlen(get_extensions_name); i++) {
+            /* Replace all non-alphanumeric characters with underscore,
+             * since they are not allowed in C symbol names. That fixes up
+             * symbol name for drivers with '-drm' suffix
+             */
+            if (!isalnum(get_extensions_name[i]))
+                get_extensions_name[i] = '_';
+        }
+
         get_extensions = dlsym(driver, get_extensions_name);
         if (get_extensions)
             extensions = get_extensions();