gdb/linux-record: Fix sizes of sigaction and sigset_t
The values were mistakenly set to size of glibc's sigset_t (128 bytes)
and sigaction (140 or 152 bytes) instead of the kernel ones. The kernel
has 4 or 8 byte old_sigset_t, 8 byte sigset_t, 16 or 32 byte old_sigaction,
20 or 32 byte sigaction.