Also recognize __sighndlr on Solaris/x86

Also recognize __sighndlr on Solaris/x86

Unlike Solaris/SPARC, the __sighndlr function isn't recognized as part
of a signal handler, causing a couple of testcases to fail.

The following patch fixes that.  A followup patch will move this to
common code to avoid such unnecessary discrepancies between
Solaris/SPARC and x86 in the future.

While this fixes a couple of backtraces to now correctly print

#1  <signal handler called>

they often fail later with

#2  0x0ff3ffffff00857f in ?? ()
Backtrace stopped: Cannot access memory at address 0xff3000002e0886f

which needs further investigation.

Tested on amd64-pc-solaris2.11 (running the tests with both -m64 and
-m32).

	* amd64-sol2-tdep.c (amd64_sol2_sigtramp_p): Also recognize
	__sighndlr.
	* i386-sol2-tdep.c (i386_sol2_sigtramp_p): Likewise.