First pass of load files through an interface (to allow loading from memory, zip file etc). So instead of posix fopen/fread, using CommonFileIOInterface.

A fileIO plugin can override custom file IO operations. As a small test, load files from a zipfile in memory.
Default fileIO implementation is in examples/Utils/b3BulletDefaultFileIO.h
Affects URDF, SDF, MJCF, Wavefront OBJ, STL, DAE, images.

examples/Importers/ImportURDFDemo/UrdfParser.cpp

@@ -2,12 +2,15 @@
 #include "../../ThirdPartyLibs/tinyxml2/tinyxml2.h"
 #include "urdfStringSplit.h"
 #include "urdfLexicalCast.h"
+#include "UrdfFindMeshFile.h"
+
 using namespace tinyxml2;
 
-UrdfParser::UrdfParser()
+UrdfParser::UrdfParser(CommonFileIOInterface* fileIO)
 	: m_parseSDF(false),
 	  m_activeSdfModel(-1),
-	  m_urdfScaling(1)
+	  m_urdfScaling(1),
+	  m_fileIO(fileIO)
 {
 	m_urdf2Model.m_sourceFile = "IN_MEMORY_STRING";  // if loadUrdf() called later, source file name will be replaced with real
 }
@@ -495,7 +498,7 @@ bool UrdfParser::parseGeometry(UrdfGeometry& geom, XMLElement* g, ErrorLogger* l
 		}
 
 		geom.m_meshFileName = fn;
-		bool success = findExistingMeshFile(
+		bool success = UrdfFindMeshFile(m_fileIO,
 			m_urdf2Model.m_sourceFile, fn, sourceFileLocation(shape),
 			&geom.m_meshFileName, &geom.m_meshFileType);
 		if (!success)