remove compare and branch in fast path for c++ operator delete[]

Summary: sdallocx is checking a flag that will never be set (at least in the provided C++ destructor implementation).  This branch will probably only rarely be mispredicted however it removes two instructions in sdallocx and one at the callsite (to zero out flags).

include/jemalloc/internal/jemalloc_internal_externs.h

@@ -51,5 +51,6 @@ void jemalloc_prefork(void);
 void jemalloc_postfork_parent(void);
 void jemalloc_postfork_child(void);
 bool malloc_initialized(void);
+void je_sdallocx_noflags(void *ptr, size_t size);
 
 #endif /* JEMALLOC_INTERNAL_EXTERNS_H */