Change the nightly ctest update command to git from svn.
Update the pre-commit source checks for the new git workflow.
Renames the private getenv implementation to our_getenv and uses the
preprocessor to redirect the core's calls to getenv() to invoke
our_getenv().  This avoids conflicts with clang's __attribute__((nonnull))
warning about our check for NULL.
Replace "> 0" comparison of monitor_data_t.trace_tag with "!= NULL" as it
is now a pointer type.
Undefine printf before defining as forbidden, to handle cases where printf
is a macro.