Add a 'starti' command.
    
    This works like 'start' but it stops at the first instruction rather
    than the first line in main().  This is useful if one wants to single
    step through runtime linker startup.
    
    While here, introduce a RUN_ARGS_HELP macro for shared help text
    between run, start, and starti.  This includes expanding the help for
    start and starti to include details from run's help text.
    
    gdb/ChangeLog:
    
    	* NEWS (Changes since GDB 8.0): Add starti.
    	* infcmd.c (enum run_break): New.
    	(run_command_1): Queue pending event for RUN_STOP_AT_FIRST_INSN
    	case.
    	(run_command): Use enum run_how.
    	(start_command): Likewise.
    	(starti_command): New function.
    	(RUN_ARGS_HELP): New macro.
    	(_initialize_infcmd): Use RUN_ARGS_HELP for run and start
    	commands.  Add starti command.
    
    gdb/doc/ChangeLog:
    
    	* gdb.texinfo (Starting your Program): Add description of
    	starti command.  Mention starti command as an alternative for
    	debugging the elaboration phase.
    
    gdb/testsuite/ChangeLog:
    
    	* gdb.base/starti.c: New file.
    	* gdb.base/starti.exp: New file.
    	* lib/gdb.exp (gdb_starti_cmd): New procedure.