build system: stop including alloca.h, stdlib.h provides it

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

scripts/basic/docproc.c

@@ -39,7 +39,7 @@
 #include <limits.h>
 #include <sys/types.h>
 #include <sys/wait.h>
-#include <alloca.h>
+//bbox disabled: #include <alloca.h>
 
 /* exitstatus is used to keep track of any failing calls to kernel-doc,
  * but execution continues. */

scripts/basic/fixdep.c

@@ -113,7 +113,7 @@
 #include <limits.h>
 #include <ctype.h>
 #include <arpa/inet.h>
-#include <alloca.h>
+//bbox disabled: #include <alloca.h>
 
 /* bbox: not needed
 #define INT_CONF ntohl(0x434f4e46)