Log Message:
devel/php-xcache: Fix errors during stage-install.

The package Makefile redefines ${EGDIR}, which was already defined
and used in lang/php/ext.mk.  Rename the package variable to
"XCACHE_EGDIR" to avoid a symbol clash.

Arguably, the EGDIR in lang/php/ext.mk should have been namespaced
a bit better to avoid conflicts with likely variable names used in
package Makefiles, e.g., PHP_EGDIR.