Fix segmentation fault caused by implicit declaration of function 'reallocarray'. Added patch will enable
reallocarray() prototype in glibc 2.26+ on Linux systems. This fix will be included in flex 2.6.5.
Fixes LEDE issue: FS#1003 (Flex does not build with GCC 7.2)
Signed-off-by: Marko Ratkaj <marko.ratkaj@sartura.hr>
