build: exclude LMDB utilities from Windows CMake build, guard POSIX includes in mplay.c

file(GLOB) in libutun/CMakeLists.txt picked up mplay.c, mdb_dump.c and other
standalone LMDB tools that are not library code and fail on Windows. Filter them
out, keep only mdb.c + midl.c.

tools/chatgui/libutun/CMakeLists.txt

@@ -9,6 +9,7 @@ set(TRANSPORT_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../transport)
 # ============================================================================
 
 file(GLOB UASYNC_SOURCES "${LIB_DIR}/*.c" "${LIB_DIR}/liblmdb/*.c")
+list(FILTER UASYNC_SOURCES EXCLUDE REGEX "/lmdb/(mtest[0-9]*\\.c|mtest\\.c|mdb_copy\\.c|mdb_dump\\.c|mdb_load\\.c|mdb_stat\\.c|mplay\\.c)$")
 
 add_library(uasync STATIC ${UASYNC_SOURCES})