Fix code comments referring to sighash

Recently we added a bunch of additional sighash types, some of the code
comments became stale. Use the non-specific term 'sighash type' instead
of a particular sighash identifier in comments to make the comments more
applicable.

src/blockdata/transaction.rs

@@ -871,7 +871,7 @@ impl EcdsaSighashType {
     pub fn to_u32(self) -> u32 { self as u32 }
 }
 
-/// Error returned when parsing `SigHashType` fails.
+/// Error returned for failure during parsing one of the sighash types.
 ///
 /// This is currently returned for unrecognized sighash strings.
 #[derive(Debug, Clone)]

src/util/psbt/error.rs

@@ -61,7 +61,7 @@ pub enum Error {
         /// Actual
         actual: Box<Transaction>,
     },
-    /// Unable to parse as a standard SigHash type.
+    /// Unable to parse as a standard sighash type.
     NonStandardSighashType(u32),
     /// Parsing errors from bitcoin_hashes
     HashParseError(hashes::Error),

src/util/psbt/mod.rs

@@ -16,7 +16,7 @@
 //!
 //! Implementation of BIP174 Partially Signed Bitcoin Transaction Format as
 //! defined at <https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki>
-//! except we define PSBTs containing non-standard SigHash types as invalid.
+//! except we define PSBTs containing non-standard sighash types as invalid.
 //!
 
 use core::cmp;

src/util/sighash.rs

@@ -645,7 +645,7 @@ impl<R: Deref<Target=Transaction>> SighashCache<R> {
         Ok(())
     }
 
-    /// Computes the legacy sighash for any SigHashType
+    /// Computes the legacy sighash for any sighash type.
     pub fn legacy_signature_hash(
         &self,
         input_index: usize,