add files.
compiles.
works.
Merge branch 'name_control' into valgrind-based

* Makefile.am: Add sources.
* gt_config.c: Add new config as string, s_only_begin_with, to record
the options.
* gt_config.h: Similar.
* gt_main.c: Make gt_thread_stack_control module takes control of
gt_thread_info_push/pop functions.
Use renamed gt_string_ functions instead of gt_init_string or gt_destory_string.
(gt_process_cmd_line_option): Responds to --only-begin-with.
(gt_print_usage): Add the help message for --only-begin-with.
* gt_string.c: Rename gt_init_string and gt_destory_string.
* gt_string.h: Similar.
* gt_thread_stack_control.c: New file. Take control of thread info
stack.
* gt_thread_stack_control.h: Similar.
* gt_time.h: Add header.