mtcp_check_vdso.c: Fixed Ubuntu 9.01 bug. glic-2.9 was more stringent about 
stack overflow errors.
others: Ububtu 9.01 uses gcc-4.3.4 -Wformat=2 which produced false positives 
warnings. We added %s format specifier to format string and empty string 
argument to eliminate warnings.
Merging Ana's latest ptrace code into unstable branch.
This creates a new bug not present in Ana's code.
As with Ana's code dmtcp make check succeeds on dmtcp1
but fails on dmtcp2. 
Ana's code successfully checkpoints and restarts gdb.
The merged code fails on checkpointing gdb ./dmtcp1.
We will find the cause and fix it soon.
This revision fixes the bug for checkpointing gdb in the previous revision.
The code should now behave the same as Ana's code. 
Like Ana's code make check fails on dmtcp in unstable branch.
Casting superior and inferior from pid_t to int for printing.
Wrapper for open and fopen added. The purpose was to fix an file open error
while opening files of type /proc/PID/status. old pid will be replaced by new 
pid in the path.
Fix Race Condition bug for ptrace code
Locking fix for DMTCP API - same as for stable branch
1. malloc/sbrk fix from main branch
2. Temp (not full) fix of GDB chackpoint/user chread race condition
Add file-based locking to fix superior checkpoint/user threads race condition.
Fix for the following problem:
- GDB run -> DMTCP checkpoint -> Ctrl+C -> GDB stepping -> GDB continue ->
  DMTCP checpoint & HANG

- Problem lies in DGB code which iterates between all threads(attached &
  detached) and stops them.
- Added code controls that at checkpoint time checkpoint thread not stopped.
  Now checkpoint threads not removed from 
- ptrace_pairs - they simply marked as already detached and ptrace_pairs is
  used in mentioned control actions.
The wrappers for dlsym and td_thr_get_info added. Needed for using next and 
step after restarting a checkpointed gdb session. If this causes a bug try
commenting out the wrapper for dlsym in pidwrappers.cpp.  Added 
REAL_PASSTHROUGH_FUNC_64 and others for wrapper with return value different
from int.
While saving the address of dlopen and dlsym in dmtcp_checkpoint.cpp there
was invalid conversion error. Putting a cast fixed the issue.
- Fix session restore logic. It was half-commented somehow. Seems that it was
  my fault. 
- Now it needs more testing. make check works well, but some of credential
  tests fails.
Fix the reason of conf5 errors
Cleaned the code for fopen and open wrappers.
Fix for GDB run -> DMTCP checkpoint -> DMTCP restart -> GDB kill -> GDB run ->
DMTCP checkpoint & PTRACE_ATTACH error.
Change to make it checkpoint gdb on 64-bit machines.
printfs converted to DPRINTF and perrors converted to mtcp_printf.
printfs caused the dmtcp2 test to fail.
With this change all tests except fork-exec are passing.