Continue fixing deadlock of previous commit, this time occuring when waiting for 'cleanup' python runtime call to finish. Now 'init' and 'cleanup' python runtime calls are called directly from main thread, and aren't anymore invoked in the context of wxMainloop and/or twisted reactor.
<xsd:attribute name="Compiler" type="xsd:string" use="optional" default="gcc"/>
<xsd:attribute name="CFLAGS" type="xsd:string" use="optional" default=""/>
<xsd:attribute name="Linker" type="xsd:string" use="optional" default="gcc"/>
<xsd:attribute name="LDFLAGS" type="xsd:string" use="optional" default=""/>