This commit allows Valgrind to be run in-place from the source tree, without
requiring "make install".  This is good for two reasons:

1. shorter compile times ("make" instead of "make install")
2. don't need to install before running the regression tests

Changes:
 - root Makefile now builds a libpthread.so.0 symlink to libpthread.so, which
   was needed.

 - startup script accepts a --in-place=<dir> option for running a non-installed
   version, where <dir> is the root of the src tree

 - VG_(mash_LD_PRELOAD_and_LD_LIBRARY_PATH) had to be fiddled with a bit

 - tests/vg_regtest now uses the --in-place option to test the non-installed
   version


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@1614 a5019735-40e9-0310-863c-91ae7b9d1cf9
4 files changed