icd: stop generating icd-dispatch-entrypoints.c

Let ICDs define XGL entrypoints directly.  This requires the Intel ICD to
rename intelSomeEntryPoint() to xglSomeEntryPoint().  In addition, the ICD
needs to be linked with -Bsymbolic to make symbol resolving work for
xglGetProcAddr().

v2: use -Bsymbolic-functions
diff --git a/icd/intel/sampler.c b/icd/intel/sampler.c
index ec46be3..0776a07 100644
--- a/icd/intel/sampler.c
+++ b/icd/intel/sampler.c
@@ -386,7 +386,7 @@
     intel_base_destroy(&sampler->obj.base);
 }
 
-XGL_RESULT XGLAPI intelCreateSampler(
+ICD_EXPORT XGL_RESULT XGLAPI xglCreateSampler(
     XGL_DEVICE                                  device,
     const XGL_SAMPLER_CREATE_INFO*              pCreateInfo,
     XGL_SAMPLER*                                pSampler)