Fix lost siginfo_t for inferior calls.
* infrun.c
(struct inferior_thread_state) <siginfo_gdbarch, siginfo_data>: New.
(save_inferior_thread_state): New variables regcache, gdbarch and
siginfo_data. Initialize SIGINFO_DATA if gdbarch_get_siginfo_type_p.
Move INF_STATE allocation later, pre-clear it. Initialize REGISTERS
using REGCACHE.
(restore_inferior_thread_state): New variables regcache and gdbarch.
Restore SIGINFO_DATA for matching GDBARCH. Restore REGISTERS using
REGCACHE. Free also SIGINFO_DATA.
gdb/testsuite/
Fix lost siginfo_t for inferior calls.
* gdb.base/siginfo-infcall.exp: New file.
* gdb.base/siginfo-infcall.c: New file.
