Compile the Windows agent with libsodium support

Download the libsodium mingw release from: https://download.libsodium.org/libsodium/releases/

Untar it in ossec-hids-*/src/external/

 @@ -646,7 +650,7 @@ $(error Do not use 'winagent' directly, use 'TARGET=winagent')
 endif
 .PHONY: winagent
 winagent:
-       ${MAKE} ${WINDOWS_BINS} CFLAGS="-DCLIENT -DWIN32 -I./${EXTERNAL_ZLIB}" LDFLAGS="-lwsock32 -lwevtapi -lshlwapi -lcomctl32 -lws2_32"
+       ${MAKE} ${WINDOWS_BINS} CFLAGS="-DCLIENT -DWIN32 -I./${EXTERNAL_ZLIB} -I./external/libsodium-win64/include -L./external/libsodium-win64/lib" LDFLAGS="-lwsock32 -lwevtapi -lshlwapi -lcomctl32 -lws2_32 -lsodium"
        cd ${EXTERNAL_LUA}src/ && ${MAKE} CC=${MING_BASE}${CC} -f Makefile.mingw mingw
        cp ${EXTERNAL_LUA}src/ossec-lua.exe win32/
        cp ${EXTERNAL_LUA}src/ossec-luac.exe win32/