[engine] Remove two replace functions from KvpValue

These were not used outside a test.

And that test was not leak free, as a result of the functions not doing
what they are supposed to do when the current value is not of the type
that is expected. (NULL is returned, but the value is not replaced)

libgnucash/engine/kvp-value.cpp

@@ -99,26 +99,6 @@ KvpValueImpl::get_type() const noexcept
     return KvpValue::Type::INVALID;
 }
 
-KvpFrame *
-KvpValueImpl::replace_frame_nc (KvpFrame * new_value) noexcept
-{
-    if (datastore.type() != type_id<KvpFrame *>())
-        return {};
-    auto ret = boost::get<KvpFrame *>(datastore);
-    datastore = new_value;
-    return ret;
-}
-
-GList *
-KvpValueImpl::replace_glist_nc (GList * new_value) noexcept
-{
-    if (datastore.type() != type_id<GList *>())
-        return {};
-    auto ret = boost::get<GList *>(datastore);
-    datastore = new_value;
-    return ret;
-}
-
 struct to_string_visitor : boost::static_visitor<void>
 {
     std::ostringstream & output;

libgnucash/engine/kvp-value.hpp

@@ -100,22 +100,6 @@ struct KvpValueImpl
      */
     ~KvpValueImpl() noexcept;
 
-    /**
-     * Replaces the frame within this KvpValueImpl.
-     *
-     * If this KvpValueImpl doesn't contain a KvpFrame, nullptr
-     * is returned. Otherwise, the old KvpFrame * is returned.
-     */
-    KvpFrame * replace_frame_nc (KvpFrame *) noexcept;
-
-    /**
-     * Replaces the glist within this KvpValueImpl.
-     *
-     * If this KvpValueImpl doesn't contain a GList, nullptr
-     * is returned. Otherwise, the old GList * is returned.
-     */
-    GList * replace_glist_nc (GList *) noexcept;
-
     /**
      * Adds another value to this KvpValueImpl.
      *

libgnucash/engine/test/test-kvp-value.cpp

@@ -30,19 +30,6 @@
 #include <memory>
 #include <gtest/gtest.h>
 
-TEST (KvpValueTest, Replace_Frame)
-{
-    auto f1 = new KvpFrameImpl;
-    std::unique_ptr<KvpValueImpl> v1 {new KvpValueImpl {f1}};
-    auto f2 = new KvpFrameImpl;
-    EXPECT_EQ (f1, v1->replace_frame_nc (f2));
-    v1->set (5.2);
-    /*f1 and f2 should be deleted now*/
-    f1 = new KvpFrameImpl;
-    EXPECT_EQ (nullptr, v1->replace_frame_nc (f1));
-    delete f1;
-}
-
 TEST (KvpValueTest, Equality)
 {
     std::unique_ptr<KvpValueImpl> v1 {new KvpValueImpl { (int64_t)1}};