Fix cannot convert 'pgm_p' to 'const void*' (fixes #1707)

extras/tests/MixedConfiguration/CMakeLists.txt

@@ -16,6 +16,7 @@ add_executable(MixedConfigurationTests
 	enable_progmem_1.cpp
 	enable_string_deduplication_0.cpp
 	enable_string_deduplication_1.cpp
+	issue1707.cpp
 	use_double_0.cpp
 	use_double_1.cpp
 )