Increase the buffer size used for the host names in wxIPaddress.

This avoids failing to set the host name if the system /etc/hosts file has any
host names that wouldn't fit in our buffer: at least under Linux/glibc,
gethostname_r() returns error if any such names exist even if we don't ask for
them.

Closes #16641.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@78505 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -577,6 +577,10 @@ Major new features in this release
 3.0.3: (released 2015-??-??)
 ----------------------------
 
+Unix:
+
+- Fix wxIPaddress::Hostname() failing if /etc/hosts contained very long names.
+
 All (GUI):
 
 - Fix several floating point rounding bugs in wxPropertyGrid (Artur Wieczorek).