- patch from Denis Vlasenko to add and use bb_xsocket() and to use

bb_xopen some more while at it.
  Also use shorter boilerplate while at it.

include/libbb.h

@@ -145,6 +145,7 @@ extern int   bb_fclose_nonstdin(FILE *f);
 extern void  bb_fflush_stdout_and_exit(int retval) ATTRIBUTE_NORETURN;
 
 extern void xstat(const char *filename, struct stat *buf);
+extern int  bb_xsocket(int domain, int type, int protocol);
 
 #define BB_GETOPT_ERROR 0x80000000UL
 extern const char *bb_opt_complementally;