IECore : Force RTLD_GLOBAL for imath

We still need to use RTLD_GLOBAL when importing imath to avoid the following error:

`TypeError: No to_python (by-value) converter found for C++ type: Imath_2_2::Vec2<float>`

Author: andrewkaufman

python/IECore/__init__.py

@@ -53,7 +53,22 @@
 		__import__( "sys" ).getdlopenflags() | __import__( "ctypes" ).RTLD_GLOBAL
 	)
 
-__import__( "imath" )
+try :
+
+	# Make sure we import imath _with_ RTLD_GLOBAL. This avoids
+	# boost to_python (by-value) converter issues for imath types.
+
+	import sys
+	import ctypes
+	originalDLOpenFlags = sys.getdlopenflags()
+	sys.setdlopenflags( originalDLOpenFlags | ctypes.RTLD_GLOBAL )
+
+	__import__( "imath" )
+
+finally :
+
+	sys.setdlopenflags( originalDLOpenFlags )
+	del sys, ctypes, originalDLOpenFlags
 
 from _IECore import *