cleanup OS detection

- the wrong variable was set for OpenBSD and Solaris
fix memory leak

- remove implicit ModuleGroup.free() call in ModuleInfo.runDtors()
- free module array passed to ModuleGroup constructor on any
  platform but Win32
Merge pull request #377 from dawgfoto/fixLeak

fix memory leak
Merge pull request #376 from dawgfoto/cleanupMakefile

cleanup OS detection
rename rt.util.string.intToString -> uintToString
Merge pull request #379 from dawgfoto/uintToString

rename rt.util.string.intToString -> uintToString
fix memory leak for core.thread.slock Mutex
Merge pull request #380 from dawgfoto/core-thread-MutexLeak

fix memory leak for core.thread.slock Mutex