Update signal handling
- Pass user readable signal name string.
- Pass signal number as exit code w/ std::exit()
- Change global signal handler name to ofSignalHandler().
Tabs to match local code style.
add mat3 uniform setter in ofShader
add note recommending 4x4 mat for shader uniform
Merge branch 'master' into feature-shader-uniform-mat3
Merge branch 'master' into feature-shader-uniform-mat3

Conflicts:
	libs/openFrameworks/gl/ofShader.h
directly access ofMatrix3x3 member when setting uniform
Merge pull request #3177 from admsyn/feature-shader-uniform-mat3

Add setter for mat3 uniforms in ofShader
fix int being used where it should be ofWindowMode

in many places, particularly setupOpenGL() and getWindowMode() methods, as well as
variables to store windowMode, the ofWindowMode enum was not being used as the type
fix RPI install_dependencies
update CHANGELOG.md for ofWindowMode, fixes #3187
Merge pull request #3189 from acarabott/bugfix-ofWindowMode

Bugfix of window mode
include ofAppBaseWindow by default. Closes #3190
addons: ofxOpenCv includes breaklines
Merge pull request #3045 from bakercp/feature-ofSigHandler

Enhanced Posix Signal Handling
Merge branch 'master' of github.com:openframeworks/openFrameworks
fixes exit sequence
fix exit callbacks
CHANGELOG exit callbacks
armv6: fix detection of RPI version when cross compiling