vm: enable filemap=1 by default

. turns on mmap() functionality for files by default
	. also causes exec() to use it to map in executables
	  without copying and with sharing those pages with the
	  disk cache and other instances of the executable

Change-Id: Idb94dfe110eed916cf83b12c45e1a77241a2cee5

test/run

@@ -29,7 +29,12 @@ alltests="   1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 \
 tests_no=`expr 0`
 
 # test mmap only if enabled in sysenv
+filemap=1	# the default is on
 if sysenv filemap >/dev/null
+then	filemap=`sysenv filemap`
+fi
+
+if [ "$filemap" -ne 0 ]
 then	alltests="$alltests 74"
 fi