Runtime: Fix bugs in Linux target.
- next occurence absolute time computation failing on 32-bit because of casting
- PLC thread was started before period was set, potentially passing uninitialized timespec to clock_nanosleep()
<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=""/>