Kconfig: CONFIG_NET_MULTILINK and CONFIG_NET_MULTINIC must be support if the loopback device and any real network device are selected

Optional canned symtab inclusion to the build. When option CONFIG_LIBC_SYMTAB is selected and symbol table file libc/symtab/canned_symtab.inc is prepared then application can use system provided complete symbol table. The option has substantial effect on system image size. Mainly code/text. If loading of applications at runtime is not planned do not select this.  From Pavel Pisa.

[PATCH] gethostbyname(): correct returned address format when DNS is used.  The hostent.h_addr_list should point to raw in_addr or in6_addr as defined in the standard. Original implementation used that
for numeric addresses but for DNS lookup returned pointer to whole sockaddr_in or sockaddr_in6.

getaddrinfo() should be preferred in a long term perspective. Return of complete addresses from the lookup would be better in such case but it requires significant changes anyway - multiple addresses support and most probably dynamic memory allocation which is bad for many RT applications. So gethostbyname() is sufficient for most applications now.

Signed-off-by: Pavel Pisa <ppisa@pikron.com>

wdogs: Fix counting of free, pre-allocated wdog timers.  The could could get decremented below zero in some situations

recvfrom(): Correct wait for new data when NET_UDP_READAHEAD is enabled.  Fix size accounting when recvfrom_udpreadahead() sets state.rf_recvlen == -1.  I have not checked if data are accumulated to the right position in the buffer however.

Signed-off-by: Pavel Pisa <ppisa@pikron.com>