Bump to exprtk submodule to latest (#4013)

plugins/Xpressive/CMakeLists.txt

@@ -10,12 +10,6 @@ SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Dexprtk_disable_rtl_io_file")
 SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Dexprtk_disable_rtl_vecops")
 SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${WERROR_FLAGS} -fexceptions")
 
-# See https://github.com/ArashPartow/exprtk/pull/9
-IF("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
-	EXECUTE_PROCESS(COMMAND patch exprtk/exprtk.hpp exprtk.hpp.patch
-	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} OUTPUT_QUIET)
-ENDIF()
-
 IF(LMMS_BUILD_WIN32 AND NOT MSVC)
 	SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wa,-mbig-obj -Dexprtk_disable_enhanced_features")
 ENDIF()

plugins/Xpressive/exprtk.hpp.patch

@@ -1,13 +0,0 @@
-diff --git a/exprtk.hpp b/exprtk.hpp
-index 916e74b..ae7de24 100644
---- a/exprtk.hpp
-+++ b/exprtk.hpp
-@@ -1962,7 +1962,7 @@ namespace exprtk
-       template <typename T>
-       inline bool string_to_real(const std::string& s, T& t)
-       {
--         const typename numeric::details::number_type<T>::type num_type;
-+         typename numeric::details::number_type<T>::type num_type;
- 
-          const char_t* begin = s.data();
-          const char_t* end   = s.data() + s.size();