[plt-scheme] 370/1 3m segfaults under linux

[John Kozak]

Running built-from-source versions of 370 and 371 under i386 and
X86_64 strains of recentish debian linux, I'm getting segfaults: after
doing an amount of I/O (reading 1000 binary files of about 2MB each),
I get a segfault, I think in GC.  I can't confirm this, because when I
try to run mzscheme under gdb, it segfaults in startup!  Any thoughts?

John