Bring back r239006 with a fix.

The fix is just that getOther had not been updated for packing the st_other
values in fewer bits and could return spurious values:

-  unsigned Other = (getFlags() & (0x3f << ELF_STO_Shift)) >> ELF_STO_Shift;
+  unsigned Other = (getFlags() & (0x7 << ELF_STO_Shift)) >> ELF_STO_Shift;

Original message:

Pack the MCSymbolELF bit fields into MCSymbol's Flags.

This reduces MCSymolfELF from 64 bytes to 56 bytes on x86_64.

While at it, also make getOther/setOther easier to use by accepting unshifted
STO_* values.

llvm-svn: 239012