build: ensure make-prime-list doesn't access out of bounds memory

build: ensure make-prime-list doesn't access out of bounds memory

The -fsanitize=address run associated with v8.22-75-gf940fec
failed to check make-prime-list, as src/primes.h is not
regenerated with `make clean`.  Running with -fsanitize=address
indicates a read 1 byte beyond the allocated buffer.

  $ rm src/make-prime-list.o
  $ make AM_CFLAGS=-fsanitize=address src/make-prime-list
  $ src/make-prime-list 5000

=================================================================
==13913==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x61e00000fa43 at pc 0x4016f5 bp 0x7fff9d9840e0 sp 0x7fff9d9840d0
READ of size 1 at 0x61e00000fa43 thread T0
    #0 0x4016f4 in main src/make-prime-list.c:214
    #1 0x7f98892c5fdf in __libc_start_main (/lib64/libc.so.6+0x1ffdf)
    #2 0x401774 (src/make-prime-list+0x401774)

0x61e00000fa43 is located 0 bytes to the right of 2499-byte
region [0x61e00000f080,0x61e00000fa43) allocated by thread T0 here:
    #0 0x7f98896ba7b7 in malloc (/lib64/libasan.so.1+0x577b7)
    #1 0x400f3f in xalloc src/make-prime-list.c:163
    #2 0x400f3f in main src/make-prime-list.c:198

SUMMARY: AddressSanitizer: heap-buffer-overflow
src/make-prime-list.c:214 main
Shadow bytes around the buggy address:
  0x0c3c7fff9ef0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3c7fff9f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3c7fff9f10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3c7fff9f20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3c7fff9f30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c3c7fff9f40: 00 00 00 00 00 00 00 00[03]fa fa fa fa fa fa fa
  0x0c3c7fff9f50: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3c7fff9f60: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3c7fff9f70: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3c7fff9f80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3c7fff9f90: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:     fa
  ...
==13913==ABORTING

* src/make-prime-list.c (main): Bounds check the incremented index,
before using to access the buffer.
Fixes http://bugs.gnu.org/19784

Change-Id: I4ef7d16b49097522350def56bf3882c6c70a17a5
Signed-off-by: Yury Usishchev <y.usishchev@samsung.com>