Audio: Don't try to fill and queue null buffer

Fixes skipping audio after interrupting and resuming
the program via eg. a debugger.
Font: Adhere to spec and set Font.default_name to "MS PGothic"
Typo
Font: Fix 'Font#set_name' not actually changing underlying TTF_Font
Font: Open TTF font as late as possible

This reduces opened fonts that were never going
to be used anyway.
Typo
Coding style fixes
Spacing
fix screen grab crash when in fullscreen

- read the FBO size NOT the screen size.
Input: Return const -20 mouse position when outside window
Bitmap: Supply image filename on loading error
Config: Fix preceeding '/' in deducted game title

Also factor out the common code path
fix npos comparison check in baseName method
Merge pull request #13 from humble/baseNameFix

Fix npos comparison check in baseName
Revert "MRI-Binding: Don't memcpy script data before deflating"

This reverts commit 7f4e58fd6ea548983b9d2fd3aaa797784011bef3.

Without this release builds on OS X fail to execute any scripts
write screenshots to desktop directory OR home directory.
implement mac OS X version of get desktop path