Fuzz tests need reproducible code, so we need an "unsafe" version of
LWIP_RAND() in this case...
Also, to reproduce fuzz tests cases from Linux on Windows,
LWIP_RAND_FOR_FUZZ_SIMULATE_GLIBC provides the first 20 random numbers that
glibc would have...
The experimental multi-packet mode splits input bytes depending on a length
decoded from the first 2 bytes and does that until the end of input.
To use this mode, compile with "make D=-DLWIP_FUZZ_MULTI_PACKET"
Signed-off-by: goldsimon <goldsimon@gmx.de>