Fast forward to sync public repo.

Compile math.sinh(), math.cosh(), math.tanh() and math.random().
Compile various io.*() functions.
Drive the GC forward on string allocations in the parser.
Improve KNUM fuse vs. load heuristics.
Add abstract C call handling to IR.

src/lj_def.h

@@ -88,6 +88,7 @@ typedef unsigned __int32 uintptr_t;
 #define checki8(x)	((x) == (int32_t)(int8_t)(x))
 #define checku8(x)	((x) == (int32_t)(uint8_t)(x))
 #define checki16(x)	((x) == (int32_t)(int16_t)(x))
+#define checku16(x)	((x) == (int32_t)(uint16_t)(x))
 
 /* Every half-decent C compiler transforms this into a rotate instruction. */
 #define lj_rol(x, n)	(((x)<<(n)) | ((x)>>(32-(n))))