Fix new Text ID usercount handling in add/load cases.

Text datablocks should always have a 'single user' flag set, and they
usually do not have any user (since neither text editor itself, nor
Freestyle usage are text users - the second is odd btw...), the only one
am aware of is the script node (e.g. for OSL).

Add text case was simply not doing anything, so added.

Load text case was doing things in inversed logic (setting user count to
zero in BKE, then setting 'real user' flag in ED code). Made it the
other way around (BKE ID creation code should not care about usercount
usually, this is up to higher-level code to decide what to do
(operators, RNA...).

Note: tried to check all cases, but there might very well be some more
hidden bugs here...

source/blender/blenkernel/intern/text.c

@@ -166,6 +166,8 @@ Text *BKE_text_add(Main *bmain, const char *name)
   Text *ta;
 
   ta = BKE_libblock_alloc(bmain, ID_TXT, name, 0);
+  /* Texts always have 'real' user (see also read code). */
+  id_us_ensure_real(&ta->id);
 
   BKE_text_init(ta);
 
@@ -354,7 +356,8 @@ Text *BKE_text_load_ex(Main *bmain, const char *file, const char *relpath, const
   }
 
   ta = BKE_libblock_alloc(bmain, ID_TXT, BLI_path_basename(filepath_abs), 0);
-  ta->id.us = 0;
+  /* Texts always have 'real' user (see also read code). */
+  id_us_ensure_real(&ta->id);
 
   BLI_listbase_clear(&ta->lines);
   ta->curl = ta->sell = NULL;

source/blender/editors/space_text/text_ops.c

@@ -241,6 +241,8 @@ static int text_new_exec(bContext *C, wmOperator *UNUSED(op))
   PropertyRNA *prop;
 
   text = BKE_text_add(bmain, "Text");
+  /* Texts have no user by default... Only the 'real' user flag. */
+  id_us_min(&text->id);
 
   /* hook into UI */
   UI_context_active_but_prop_get_templateID(C, &ptr, &prop);
@@ -307,6 +309,8 @@ static int text_open_exec(bContext *C, wmOperator *op)
   RNA_string_get(op->ptr, "filepath", str);
 
   text = BKE_text_load_ex(bmain, str, BKE_main_blendfile_path(bmain), internal);
+  /* Texts have no user by default... Only the 'real' user flag. */
+  id_us_min(&text->id);
 
   if (!text) {
     if (op->customdata) {
@@ -322,8 +326,6 @@ static int text_open_exec(bContext *C, wmOperator *op)
   /* hook into UI */
   pprop = op->customdata;
 
-  id_us_ensure_real(&text->id);
-
   if (pprop->prop) {
     RNA_id_pointer_create(&text->id, &idptr);
     RNA_property_pointer_set(&pprop->ptr, pprop->prop, idptr, NULL);

source/blender/makesrna/intern/rna_main_api.c

@@ -555,6 +555,8 @@ static Text *rna_Main_texts_load(Main *bmain,
 
   errno = 0;
   txt = BKE_text_load_ex(bmain, filepath, BKE_main_blendfile_path(bmain), is_internal);
+  /* Texts have no user by default... Only the 'real' user flag. */
+  id_us_min(&txt->id);
 
   if (!txt) {
     BKE_reportf(reports,