Required in order to build with Studio cc now that xorg-macros is
setting -errwarn=E_FUNC_HAS_NO_RETURN_STMT since a bug in the Solaris
system headers causes the noreturn attribute to not be correctly
applied to the exit() prototype in <stdlib.h> when building with
Studio instead of gcc.

Otherwise compiler exits with errors:
"Display.c", line 65: Function has no return statement : x_io_error_handler
"hostx.c", line 341: Function has no return statement : x_io_error_handler

Uses Studio-specific pragma instead of adding another exit() prototype
with a noreturn attribute to avoid causing gcc to warn about having
a redundant prototype for the exit() function.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Mikhail Gusarov <dottedmag@dottedmag.net>