Main runtime template C code : Added HAVE_RETAIN preprocessor definition for customized build to signal it provides IEC-61131 Retain memory handling function. Removed targets/Xenomai/plc_Xenomai_noretain.c, now useless.
<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=""/>