reintroduce thread analysis but disable it for backwards compatibility

compiler/options.nim

@@ -60,6 +60,7 @@ type                          # please make sure we have under 32 options
     optContext,               # ideTools: 'context'
     optDef,                   # ideTools: 'def'
     optUsages,                # ideTools: 'usages'
+    optThreadAnalysis,        # thread analysis pass
     optTaintMode,             # taint mode turned on
     optTlsEmulation,          # thread var emulation turned on
     optGenIndex               # generate index file for documentation;