libc: only have one select implementation, and move the pollfds onto the heap if they cross some threshold

@@ -560,11 +560,10 @@
         rewinddir.o             \
         rindex.o                \
         scandir.o               \
         seekdir.o               \
         select.o                \
-        select_large_fdset.o    \
         setlabel.o              \
         setpriority.o           \
         settimeofday.o          \
         sh_locks.o              \
         sigflag.o               \