dead code: Remove dead option in HexStr conversion

Problem:
- Nothing uses the `fspaces` argument to `HexStr()` besides unit
  tests. This argument results in extra complexity and a small
  performance decrease within the function for branch evalulation.

Solution:
- Remove unused `fspaces` option.

src/test/util_tests.cpp

@@ -77,80 +77,40 @@ BOOST_AUTO_TEST_CASE(util_HexStr)
         HexStr(ParseHex_expected, ParseHex_expected + sizeof(ParseHex_expected)),
         "04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f");
 
-    BOOST_CHECK_EQUAL(
-        HexStr(ParseHex_expected, ParseHex_expected + 5, true),
-        "04 67 8a fd b0");
-
     BOOST_CHECK_EQUAL(
         HexStr(ParseHex_expected + sizeof(ParseHex_expected),
                ParseHex_expected + sizeof(ParseHex_expected)),
         "");
 
-    BOOST_CHECK_EQUAL(
-        HexStr(ParseHex_expected + sizeof(ParseHex_expected),
-               ParseHex_expected + sizeof(ParseHex_expected), true),
-        "");
-
     BOOST_CHECK_EQUAL(
         HexStr(ParseHex_expected, ParseHex_expected),
         "");
 
-    BOOST_CHECK_EQUAL(
-        HexStr(ParseHex_expected, ParseHex_expected, true),
-        "");
-
     std::vector<unsigned char> ParseHex_vec(ParseHex_expected, ParseHex_expected + 5);
 
-    BOOST_CHECK_EQUAL(
-        HexStr(ParseHex_vec, true),
-        "04 67 8a fd b0");
-
     BOOST_CHECK_EQUAL(
         HexStr(ParseHex_vec.rbegin(), ParseHex_vec.rend()),
         "b0fd8a6704"
     );
 
-    BOOST_CHECK_EQUAL(
-        HexStr(ParseHex_vec.rbegin(), ParseHex_vec.rend(), true),
-        "b0 fd 8a 67 04"
-    );
-
     BOOST_CHECK_EQUAL(
         HexStr(std::reverse_iterator<const uint8_t *>(ParseHex_expected),
                std::reverse_iterator<const uint8_t *>(ParseHex_expected)),
         ""
     );
 
-    BOOST_CHECK_EQUAL(
-        HexStr(std::reverse_iterator<const uint8_t *>(ParseHex_expected),
-               std::reverse_iterator<const uint8_t *>(ParseHex_expected), true),
-        ""
-    );
-
     BOOST_CHECK_EQUAL(
         HexStr(std::reverse_iterator<const uint8_t *>(ParseHex_expected + 1),
                std::reverse_iterator<const uint8_t *>(ParseHex_expected)),
         "04"
     );
 
-    BOOST_CHECK_EQUAL(
-        HexStr(std::reverse_iterator<const uint8_t *>(ParseHex_expected + 1),
-               std::reverse_iterator<const uint8_t *>(ParseHex_expected), true),
-        "04"
-    );
-
     BOOST_CHECK_EQUAL(
         HexStr(std::reverse_iterator<const uint8_t *>(ParseHex_expected + 5),
                std::reverse_iterator<const uint8_t *>(ParseHex_expected)),
         "b0fd8a6704"
     );
 
-    BOOST_CHECK_EQUAL(
-        HexStr(std::reverse_iterator<const uint8_t *>(ParseHex_expected + 5),
-               std::reverse_iterator<const uint8_t *>(ParseHex_expected), true),
-        "b0 fd 8a 67 04"
-    );
-
     BOOST_CHECK_EQUAL(
         HexStr(std::reverse_iterator<const uint8_t *>(ParseHex_expected + 65),
                std::reverse_iterator<const uint8_t *>(ParseHex_expected)),

src/util/strencodings.h

@@ -12,6 +12,7 @@
 #include <attributes.h>
 
 #include <cstdint>
+#include <iterator>
 #include <string>
 #include <vector>
 
@@ -121,28 +122,25 @@ NODISCARD bool ParseUInt64(const std::string& str, uint64_t *out);
 NODISCARD bool ParseDouble(const std::string& str, double *out);
 
 template<typename T>
-std::string HexStr(const T itbegin, const T itend, bool fSpaces=false)
+std::string HexStr(const T itbegin, const T itend)
 {
     std::string rv;
     static const char hexmap[16] = { '0', '1', '2', '3', '4', '5', '6', '7',
                                      '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
-    rv.reserve((itend-itbegin)*3);
+    rv.reserve(std::distance(itbegin, itend) * 2);
     for(T it = itbegin; it < itend; ++it)
     {
         unsigned char val = (unsigned char)(*it);
-        if(fSpaces && it != itbegin)
-            rv.push_back(' ');
         rv.push_back(hexmap[val>>4]);
         rv.push_back(hexmap[val&15]);
     }
-
     return rv;
 }
 
 template<typename T>
-inline std::string HexStr(const T& vch, bool fSpaces=false)
+inline std::string HexStr(const T& vch)
 {
-    return HexStr(vch.begin(), vch.end(), fSpaces);
+    return HexStr(vch.begin(), vch.end());
 }
 
 /**