New code assist API

This is a re-work of our completion engine. Primary goals are:

- Allow the computation to run in a separate thread so the GUI is not locked.
- Support a model-based approach. QStrings are still needed (filtering, etc), but
internal structures are free to use more efficient representations.
- Unifiy all kinds of *assist* into a more reusable and extensible framework.
- Remove unnecessary dependencies on the text editor so we have more generic
and easily "plugable" components (still things to be resolved).

src/plugins/glsleditor/glsleditor.cpp

@@ -37,6 +37,7 @@
 #include "glslhighlighter.h"
 #include "glslautocompleter.h"
 #include "glslindenter.h"
+#include "glslcompletionassist.h"
 
 #include <glsl/glsllexer.h>
 #include <glsl/glslparser.h>
@@ -412,3 +413,17 @@ Document::Ptr GLSLTextEditorWidget::glslDocument() const
 {
     return m_glslDocument;
 }
+
+TextEditor::IAssistInterface *GLSLTextEditorWidget::createAssistInterface(
+    TextEditor::AssistKind kind,
+    TextEditor::AssistReason reason) const
+{
+    if (kind == TextEditor::Completion)
+        return new GLSLCompletionAssistInterface(document(),
+                                                 position(),
+                                                 editor()->file(),
+                                                 reason,
+                                                 mimeType(),
+                                                 glslDocument());
+    return BaseTextEditorWidget::createAssistInterface(kind, reason);
+}