message: [Trivial] Placate clang warning string-plus-int
  Replace eg `"tv"+2` with the suggested syntax of `&"tv"[2]`.
diff: @@ -301,8 +301,8 @@ public:
  nZerocoinAccount = 100000;
  //sv for "stealth veil" & bv for "basecoin veil"
  - bech32Prefixes[STEALTH_ADDRESS].assign("sv","sv"+2);
  - bech32Prefixes[BASE_ADDRESS].assign("bv", "bv"+2);
  + bech32Prefixes[STEALTH_ADDRESS].assign("sv",&"sv"[2]);
  + bech32Prefixes[BASE_ADDRESS].assign("bv", &"bv"[2]);
  bech32_hrp_stealth = "sv";
  bech32_hrp_base = "bv";
  @@ -491,8 +491,8 @@ public:
  base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};
  base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};
  - bech32Prefixes[STEALTH_ADDRESS].assign("tps","tps"+3);
  - bech32Prefixes[BASE_ADDRESS].assign("tv", "tv"+2);
  + bech32Prefixes[STEALTH_ADDRESS].assign("tps",&"tps"[3]);
  + bech32Prefixes[BASE_ADDRESS].assign("tv", &"tv"[2]);
  nBIP44ID = 0x80000001;
  nRingCTAccount = 20000;
  nZerocoinAccount = 100000;
  @@ -662,8 +662,8 @@ public:
  base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};
  base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};
  - bech32Prefixes[STEALTH_ADDRESS].assign("tps","tps"+3);
  - bech32Prefixes[BASE_ADDRESS].assign("tv", "tv"+2);
  + bech32Prefixes[STEALTH_ADDRESS].assign("tps",&"tps"[3]);
  + bech32Prefixes[BASE_ADDRESS].assign("tv", &"tv"[2]);
  nBIP44ID = 0x80000001;
  nRingCTAccount = 20000;
  nZerocoinAccount = 100000;
  @@ -832,8 +832,8 @@ public:
  base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};
  base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};
  - bech32Prefixes[STEALTH_ADDRESS].assign("tps","tps"+3);
  - bech32Prefixes[BASE_ADDRESS].assign("tv", "tv"+2);
  + bech32Prefixes[STEALTH_ADDRESS].assign("tps", &"tps"[3]);
  + bech32Prefixes[BASE_ADDRESS].assign("tv", &"tv"[2]);
  nBIP44ID = 0x80000001;
  nRingCTAccount = 20000;
  nZerocoinAccount = 100000;
  