Performance timer tweaks

- moved performance counter and drawing to separate file
- tweaks to performance drawing
Renamed FPScounter to PerfGraph

- Renamed FPScounter to PerfGraph
- dump avg times at exit
Moving variables at top of blocks for better VC support
Update nanovg.c
Merge pull request #34 from Nairou/patch-1

Remaining change for VC support
Improve VC support
Merge pull request #35 from Nairou/master

Improve VC support
Update windows build settings as discussed in issue #24
Reset pixel storage settings after load texture.
Another reset pixel storage settings after load texture.
Merge pull request #36 from dougbinks/master

Reset pixel storage settings after load texture.
reduces warnings