[binutils-gdb] Fix build breakage from last commit (window-nat.c:windows_create_inferior)

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 5430098f1807e084fe4ff5057040d68435f3d8a2 ***

Author: Sergio Durigan Junior <sergiodj@redhat.com>
Branch: master
Commit: 5430098f1807e084fe4ff5057040d68435f3d8a2

Fix build breakage from last commit (window-nat.c:windows_create_inferior)

Forgot to declare the variable 'toexec' (from
window-nat.c:windows_create_inferior) as 'const char *', which caused
a build breakage.

gdb/ChangeLog:
2017-04-12  Sergio Durigan Junior  <sergiodj@redhat.com>

	* windows-nat.c (windows_create_inferior): Declare 'toexec' as
	'const char *'.