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/cmd_prepare.c b/icd/intel/cmd_prepare.c
index 61937a2..f52721f 100644
--- a/icd/intel/cmd_prepare.c
+++ b/icd/intel/cmd_prepare.c
@@ -163,7 +163,7 @@
     return flags;
 }
 
-XGL_VOID XGLAPI intelCmdPrepareMemoryRegions(
+ICD_EXPORT XGL_VOID XGLAPI xglCmdPrepareMemoryRegions(
     XGL_CMD_BUFFER                              cmdBuffer,
     XGL_UINT                                    transitionCount,
     const XGL_MEMORY_STATE_TRANSITION*          pStateTransitions)
@@ -185,7 +185,7 @@
     cmd_batch_flush(cmd, flush_flags);
 }
 
-XGL_VOID XGLAPI intelCmdPrepareImages(
+ICD_EXPORT XGL_VOID XGLAPI xglCmdPrepareImages(
     XGL_CMD_BUFFER                              cmdBuffer,
     XGL_UINT                                    transitionCount,
     const XGL_IMAGE_STATE_TRANSITION*           pStateTransitions)