Lower heap size limits on systems that are short of virtual memory.

src/platform-posix.cc

Index: src/platform-posix.cc
===================================================================
--- src/platform-posix.cc	(revision 8132)
+++ src/platform-posix.cc	(working copy)
@@ -54,6 +54,18 @@
 namespace v8 {
 namespace internal {
 
+
+// Maximum size of the virtual memory.  0 means there is no artificial
+// limit.
+
+intptr_t OS::MaxVirtualMemory() {
+  struct rlimit limit;
+  int result = getrlimit(RLIMIT_DATA, &limit);
+  if (result != 0) return 0;
+  return limit.rlim_cur;
+}
+
+
 // ----------------------------------------------------------------------------
 // Math functions