vdoc: cleanup warnings on `./v doc -s vlib`

vlib/live/sharedlib/live_sharedlib.v

@@ -3,5 +3,5 @@ module sharedlib
 import live
 
 pub const (
-	is_used = 1
+	is_used = live.is_used + 1
 )

vlib/math/big/big.v

@@ -76,7 +76,7 @@ pub fn (n Number) str() string {
 }
 
 pub fn (n Number) hexstr() string {
-	mut buf := [8192]byte
+	mut buf := [8192]byte{}
 	C.bignum_to_string( &n, buf, 8192)
 	// NB: bignum_to_string , returns the HEXADECIMAL representation of the bignum n
 	s := tos_clone( buf )