Add include of stdint.h for int32_t

File addsynth.h was missing an include of <stdint.h> before using int32_t,
and aeolus.h was incorrectly specifying "stdint.h" instead of <stdint.h>
(this was not evident in all build environments).
Merge pull request #220 from softins/fix-stdint-in-aeolus

Add include of stdint.h for int32_t