runtime: handle DW_EH_PE_absptr in type table encoding

The type table encoding can be DW_EH_PE_absptr, but this case
    was missing, which was causing abort on ARM32 EABI. Add the
    missing case.
    
    Reviewed-on: https://go-review.googlesource.com/c/153857

From-SVN: r267070

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-be6dbbdbe29f39d6d2ec0d5574ced398cb6e250a
+16a48dbc1c69075321b388d235651b59abcb58ce
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/runtime/go-unwind.c

@@ -318,6 +318,8 @@ value_size (uint8_t encoding)
       case DW_EH_PE_sdata8:
       case DW_EH_PE_udata8:
         return 8;
+      case DW_EH_PE_absptr:
+        return sizeof(uintptr);
       default:
         break;
     }