[MoarVM Bump] Brings 12 commits

MoarVM bump brought: MoarVM/MoarVM@2018.03...2018.03-12-gb5b6968
b5b6968 Fix "'optimize_iffy' : not all control paths return a value"
67056c2 Fix optimization of zombie conditional causing segfault
a3bd17b Fix windows1252/1 decodestream replacement with last pos repl.
dd2072d Fix missing `:` in ChangeLog, causing website not to generate right
41711ff Make sure shiftjis_codeindex.h is added to Makefile.in
5a40729 Fix buffer overflow in shiftjis encode
a14ecc1 Implement ShiftJIS encode support
9ce054d Update generate_encoding_codetables.p6 to gen shiftjis switch
b03c8fd Have UCD-Download also download Shift-JIS code index
2bd6915 Fix segfault on concurrent array access while resizing
63348dc insert null-out-instructions before prof_enter
ed4ed0e metadata for ReentrantMutex and Semaphore

tools/build/MOAR_REVISION

@@ -1 +1 @@
-2018.03
+2018.03-12-gb5b6968