BUG #2406: Not all systems support SHM_SHARE_MMU

["Paul van der Zwan" <paul(dot)vanderzwan(at)sun(dot)com>]

The following bug has been logged online:

Bug reference:      2406
Logged by:          Paul van der Zwan
Email address:      paul(dot)vanderzwan(at)sun(dot)com
PostgreSQL version: 8.1.3
Operating system:   Solaris
Description:        Not all systems support SHM_SHARE_MMU
Details: 

Only systems with large pagesizes support ISM, so always defining 
#define PG_SHMAT_FLAGS                  SHM_SHARE_MMU
in src/backend/port/sysv_shmem.c  will cause all calls to shmat to fail with
EINVAL on systems that do not support large pages.
The following may be a better check:
#if def SHM_SHARE_MMU
#define PG_SHMAT_FLAGS ((getpagesizes(0,NULL)>1)?SHM_SHARE_MMU:0)
#else
#define PG_SHMAT_FLAGS 0
#endif

This problem manifested itself on a VIA Mini ITX system and Solaris Nevada (
build 36) 

 Paul van der Zwan