jigsaw startup memory requirements

[Martin Buchholz]

Latest jigsaw b83 works well with the temporary hacks we have in place in
jsr166 CVS, but we do see one jtreg test failure.

Running a modern jdk with only -Xmx2m is pushing it, but you probably don't
want to arbitrarily increase jdk memory requirements just for jigsaw.

Should be bump up the -Xmx in this test or wait for y'all-dev to reduce
memory footprint?

util/concurrent/ConcurrentLinkedQueue/RemoveLeak.java

command: main -Xmx2m RemoveLeak
reason: User specified action: run main/othervm -Xmx2m RemoveLeak
elapsed time (seconds): 0.302
STDOUT:
Error occurred during initialization of VM
java.lang.OutOfMemoryError: Java heap space
at java.lang.module.ModuleInfo.readIgnoringHashes(java.base at 9.0
/ModuleInfo.java:128)
at java.lang.module.InstalledModuleFinder.<clinit>(java.base at 9.0
/InstalledModuleFinder.java:96)
at java.lang.module.ModuleFinder.ofInstalled(java.base at 9.0
/ModuleFinder.java:141)
at jdk.internal.module.ModuleBootstrap.boot(java.base at 9.0
/ModuleBootstrap.java:79)
at java.lang.System.initPhase2(java.base at 9.0/System.java:1243)