Bug#25048128: MAP_NORESERVE NO LONGER DEFINED IN FREEBSD 11

MAP_NORESERVE is no longer defined on FreeBSD 11
which breaks the build.

Fix: Reintroduce code from 5.6 that defines MAP_NORESERVE to 0
if it doesn't exist.

Change-Id: I22daeeca0584ed1d21c12135e9a1a166ce31cc07
(cherry picked from commit 249c59163a797ede2d77e9e3c3e05940e1f55087)

Author: jhauglid

include/my_sys.h

@@ -855,6 +855,14 @@ extern my_bool my_gethwaddr(uchar *to);
 #define MAP_NOSYNC      0
 #endif
 
+/*
+  Not defined in FreeBSD 11.
+  Was never implemented in FreeBSD, so we just set it to 0.
+*/
+#ifndef MAP_NORESERVE
+#define MAP_NORESERVE 0
+#endif
+
 #ifdef HAVE_MMAP64
 #define my_mmap(a,b,c,d,e,f)    mmap64(a,b,c,d,e,f)
 #else