IPRT/SUPDrv/VMM: Made RTR0AssertPanicSystem available to VMMR0.r0 on darwin & solaris (only platforms implemting it currently). Created RTAssertMsg1, RTAssertMsg2 and RTAssertMsg2V (darwin only atm) in addition to AssertMsg1/2 and delcared the latter two as weak and overridable by users, while the former are strong and exposed by SUPDrv. This way we can get the full assertion text in the 'Problem Report for Mac OS X Kernel' thing. Will propagte the changes to the other platforms and rings later.