Added include of stdlib.h because malloc needs it to work. Malloc time to time fails in server/core/buffer.c and produces the following error:

*** Error in `./maxscale': malloc(): memory corruption (fast): 0x00007f3988005510 ***
======= Backtrace: =========
/lib64/libc.so.6(+0x7afc6)[0x7f39c67a9fc6]
/lib64/libc.so.6(+0x7d245)[0x7f39c67ac245]
/lib64/libc.so.6(__libc_malloc+0x63)[0x7f39c67ad633]
./maxscale(gwbuf_alloc+0x34)[0x406250]
/home/raatikka/bin/tmp/MaxScale/modules/libMySQLClient.so(MySQLSendHandshake+0x19b)[0x7f39afb09bc0]
/home/raatikka/bin/tmp/MaxScale/modules/libMySQLClient.so(+0x4d1b)[0x7f39afb0ad1b]
./maxscale(poll_waitevents+0x42a)[0x40d0c3]
/lib64/libpthread.so.0(+0x7e0f)[0x7f39c6ae5e0f]
/lib64/libc.so.6(clone+0x6d)[0x7f39c681844d]
======= Memory map: ========
00400000-0041a000 r-xp 00000000 08:03 6686345                            /home/raatikka/bin/tmp/bin/maxscale
00619000-0061a000 r--p 00019000 08:03 6686345                            /home/raatikka/bin/tmp/bin/maxscale
0061a000-0061b000 rw-p 0001a000 08:03 6686345                            /home/raatikka/bin/tmp/bin/maxscale
012fa000-0141e000 rw-p 00000000 00:00 0                                  [heap]
7f3984000000-7f3984021000 rw-p 00000000 00:00 0 

- and so forth.

utils/skygw_debug.h

@@ -17,6 +17,7 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <assert.h>
 
 #define __USE_UNIX98 1