Implemented a more systematic approach for intercepting POSIX threads

Implemented a more systematic approach for intercepting POSIX threads
functions: for each function name to intercept, intercept the function
name itself, the function name with @* appended (versioned symbols on
Linux) and the function name with $* appended (versioned symbols on
Darwin). Updated filter_stderr such that symbol versions are removed.
Updated the expected output files that contain names of intercepted
functions.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@10679