Merge #902: util::amount: Make from_sat constructor constant

31571ca util::amount: Make from_sat constructor constant (Steven Roose)

Pull request description:

  Currently unmergable because of MSRV but I heard talk about bumping it, so once it's bumped, this is a very much needed change :)

ACKs for top commit:
  tcharding:
    ACK 31571ca
  apoelstra:
    ACK 31571ca

Tree-SHA512: f254eb10a4349d890e29ea5fae77536429c7e731362cf2edcf2fe98ec9cbf2d8bbf65f98dfc8f0b80bac89960de688005d066a116d6cb62cca1efa9c1151f2ae

src/util/amount.rs

@@ -346,7 +346,7 @@ impl Amount {
     pub const MAX_MONEY: Amount = Amount(21_000_000 * 100_000_000);
 
     /// Create an [Amount] with satoshi precision and the given number of satoshis.
-    pub fn from_sat(satoshi: u64) -> Amount {
+    pub const fn from_sat(satoshi: u64) -> Amount {
         Amount(satoshi)
     }
 
@@ -633,7 +633,7 @@ impl SignedAmount {
     pub const MAX_MONEY: SignedAmount = SignedAmount(21_000_000 * 100_000_000);
 
     /// Create an [SignedAmount] with satoshi precision and the given number of satoshis.
-    pub fn from_sat(satoshi: i64) -> SignedAmount {
+    pub const fn from_sat(satoshi: i64) -> SignedAmount {
         SignedAmount(satoshi)
     }