ios develop fixes

- added ofXml to ios openframeworks xcode project
- fixed small compiler bug with ofLogWarning
Merge pull request #2288 from julapy/ios-develop-fixes

ios develop fixes
ofXml.cpp: fix crash on empty documents when setting values
linux: fix errors from logging commits
linux: fix all warnings
androidGuiExample + couple of fixes for ofxGui on small screens
ofUtils.cpp: fix ofToDataPath for android
ofTexture: add npot detection for GLES
ofxGui: disable texture hack before drawing load/save icons
OFAndroidWindow: fix bg flicker on start
ofRectRounded: wasn't clearing the shape creating a leak + ofPath rectrounded should close the shape
ofPArameter & ofxGui: fix listener methods to work with bool returning listeners
Merge branch 'develop' of https://github.com/openframeworks/openFrameworks.git into develop