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/shader.c b/icd/intel/shader.c
index 4546cd6..2480cf1 100644
--- a/icd/intel/shader.c
+++ b/icd/intel/shader.c
@@ -70,7 +70,7 @@
     return XGL_SUCCESS;
 }
 
-XGL_RESULT XGLAPI intelCreateShader(
+ICD_EXPORT XGL_RESULT XGLAPI xglCreateShader(
         XGL_DEVICE                                  device,
         const XGL_SHADER_CREATE_INFO*               pCreateInfo,
         XGL_SHADER*                                 pShader)