configure.ac: fix configure tests broken with Clang 15 (implicit function declarations)
Clang 15 makes implicit function declarations fatal by default which
leads to some of tcpdump's configure tests silently failing/returning
the wrong result.
This adds the needed #includes to various tests for the functions used,
resolving the following errors:
```
net-analyzer/tcpdump-4.99.1/clang15.log:47:error: type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int [-Wimplicit-int]
net-analyzer/tcpdump-4.99.1/clang15.log:51:error: call to undeclared library function 'strcmp' with type 'int (const char *, const char *)'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
net-analyzer/tcpdump-4.99.1/clang15.log:55:error: call to undeclared library function 'sscanf' with type 'int (const char *restrict, const char *restrict, ...)'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
net-analyzer/tcpdump-4.99.1/clang15.log:68:error: call to undeclared library function 'memset' with type 'void *(void *, int, unsigned long)'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
net-analyzer/tcpdump-4.99.1/clang15.log:112:error: call to undeclared function 'ether_ntohost'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
net-analyzer/tcpdump-4.99.1/clang15.log:115:error: call to undeclared library function 'exit' with type 'void (int) __attribute__((noreturn))'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
```
Signed-off-by: Sam James <[email protected]>
projects / tcpdump / commit
