Rebase to FSF GDB 7.2.50.20110320 (which is a 7.3 pre-release).

Merge archer-sergiodj-stap, the SystemTap probes breakpoints feature.
[stap] Fix -O2 warnings.
Fix Ada support crash on uninitialized gdbarch.

gdb-6.3-bz202689-exec-from-pthread-test.patch

@@ -92,7 +92,7 @@
 +gdb_run_cmd
 +
 +gdb_test_multiple {} "Program exited" {
-+   -re "\r\nProgram exited normally.\r\n$gdb_prompt $" {
++   -re "\r\n\\\[Inferior .* exited normally\\\]\r\n$gdb_prompt $" {
 +       pass "Program exited"
 +   }
 +}