PDF: Add text support with a font framework (font embedding to come).

PDF: Add text support with a font framework (font embedding to come).

Supports fakeBold, underline, strikethrough, mode (fill, stroke, both), size, skew, alignment (left, center, right).
Missing is drawFontOnPath and font lookup and embedding.
Changed SkPDFString to support how it is used from drawText methods.
Moved compile assert into SkTypes.
Moved constants and utility function used to support fakeBold, underline, and strikethrough into higher level locations.

Review URL: http://codereview.appspot.com/2946041

git-svn-id: http://skia.googlecode.com/svn/trunk@624 2bbb7eff-a529-9590-31e7-b0007b416f81