IDE: Fix missing highlighted element in diagrams when using GTK3

- wx's logical function does not work on gtk3, and highlighting relies on it
- skipping logical funciion at all "works" but this now makes highlight opaque
- no easy fix for highlight transparency since emulated with AND Wx logical function
+ added other highlight related cosmetic fix.

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                  <xsd:element name="Xenomai">

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                    <xsd:complexType>

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                      %(toolchain_gcc)s

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                      <xsd:attribute name="XenoConfig" type="xsd:string" use="optional" default="xeno-config"/>

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                    </xsd:complexType>

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                  </xsd:element>