add nqp::isbig_I op, and nqp:: variants for bigint <-> str conversion

src/PAST/NQP.pir

@@ -561,6 +561,11 @@ entry to produce the node to be returned.
     maphash['isgt_s']   = 'isgt__Iss'
     maphash['isge_s']   = 'isge__Iss'
 
+    # bigint ops
+    maphash['fromstr_I'] = 'nqp_bigint_from_str__PPs'
+    maphash['tostr_I']   = 'nqp_bigint_to_str__SP'
+    maphash['isbig_I']   = 'nqp_bigint_is_big__IP'
+
     # boolean opcodes
     maphash['not_i']    = 'not__Ii'
 

src/ops/nqp_bigint.ops

@@ -379,3 +379,9 @@ inline op nqp_bigint_pow(out PMC, in PMC, in PMC, in PMC) :base_core {
     }
 }
 
+/* returns 1 if $2 is too large to fit into an INTVAL without loss of
+   information */
+inline op nqp_bigint_is_big(out INT, in PMC) :base_core {
+    mp_int  *a = get_bigint(interp, $2);
+    $1 = a->used > 1;
+}

t/nqp/60-bigint.t

@@ -3,8 +3,6 @@ use nqpmo;
 
 plan(22);
 
-pir::nqp_bigint_setup__v();
-
 my $knowhow := pir::get_knowhow__P();
 my $bi_type := $knowhow.new_type(:name('TestBigInt'), :repr('P6bigint'));
 $bi_type.HOW.compose($bi_type);