Merge from the trunk, a bunch of improvements for exp-ptrcheck:

Merge from the trunk, a bunch of improvements for exp-ptrcheck:

8908  Add some more system calls to ptrcheck.

9027  Ptrcheck: More aggressive suppression of error reports from ld.so.

9056  Handle a few more syscalls, as per #179618.

9059  Prior to this commit, exp-ptrcheck would assert if the DWARF3
      data for global or stack blocks described overlapping blocks

9060  Intercept and replace calls to calls to strnlen in glibc, for the
      usual reasons.

9061  Minor refinements:
      * h_main.c: handle a few more syscalls
      * exp-ptrcheck.supp: ignore errors in glibc's getenv
        -- is highly optimised
      * pc_common.c: fix small error in error message printing

9062  Remove function that was made redundant by r9059.

git-svn-id: svn://svn.valgrind.org/valgrind/branches/VALGRIND_3_4_BRANCH@9077