Internal version dependencies cleanup (#5401)

* always depend on latest alpha version

* integrate arithmetic fuzzer into root workspace

substrate/Cargo.lock

@@ -125,6 +125,12 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "arbitrary"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "75153c95fdedd7db9732dfbfc3702324a1627eec91ba56e37cd0ac78314ab2ed"
+
 [[package]]
 name = "arc-swap"
 version = "0.4.4"
@@ -2072,6 +2078,17 @@ dependencies = [
  "hmac",
 ]
 
+[[package]]
+name = "honggfuzz"
+version = "0.5.47"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3de2c3273ef7735df1c5a72128ca85b1d20105b9aac643cdfd7a6e581311150"
+dependencies = [
+ "arbitrary",
+ "lazy_static",
+ "memmap",
+]
+
 [[package]]
 name = "http"
 version = "0.1.21"
@@ -3183,6 +3200,16 @@ version = "2.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3728d817d99e5ac407411fa471ff9800a778d88a24685968b36824eaf4bee400"
 
+[[package]]
+name = "memmap"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6585fd95e7bb50d6cc31e20d4cf9afb4e2ba16c5846fc76793f11218da9c475b"
+dependencies = [
+ "libc",
+ "winapi 0.3.8",
+]
+
 [[package]]
 name = "memoffset"
 version = "0.5.3"
@@ -7105,6 +7132,17 @@ dependencies = [
  "sp-std",
 ]
 
+[[package]]
+name = "sp-arithmetic-fuzzer"
+version = "2.0.0-alpha.5"
+dependencies = [
+ "honggfuzz",
+ "num-bigint",
+ "num-traits",
+ "primitive-types",
+ "sp-arithmetic",
+]
+
 [[package]]
 name = "sp-authority-discovery"
 version = "2.0.0-alpha.5"
@@ -8676,7 +8714,7 @@ version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3bfd5b7557925ce778ff9b9ef90e3ade34c524b5ff10e239c69a42d546d2af56"
 dependencies = [
- "rand 0.6.5",
+ "rand 0.7.3",
 ]
 
 [[package]]