Check every word in docs

This enables checking all text to see if it
either represents a valid reference or is a
word in docs/spelling.txt . Expressions are
checked for validity as well.

There are a few shortcuts (marked with TODO):
- typedefs aren't resolved, so cheats are
added for SkVector and SkIVector.
- operator overload detection is incomplete
- constructor detection is incomplete
- formula definitions aren't detected

Found and fixed a bunch of spelling, usage,
and incorrect or obsolete references.

A few comment changes are needed in
include/core to get this to work, mostly
centered around recent SkPaint/SkFont edits.

TBR=reed@google.com
Docs-Preview: https://skia.org/?cl=167541
Bug: skia:
Change-Id: I2e0d5990105c5a8482b0c0d3e50fd0b330996dd6
Reviewed-on: https://skia-review.googlesource.com/c/167541
Reviewed-by: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
diff --git a/docs/SkColor_Reference.bmh b/docs/SkColor_Reference.bmh
index 82f6d60..e3efad4 100644
--- a/docs/SkColor_Reference.bmh
+++ b/docs/SkColor_Reference.bmh
@@ -714,7 +714,7 @@
 
 # ------------------------------------------------------------------------------
 
-#Subtopic PMColor
+#Subtopic PM_Color
 #Line # color components premultiplied by Alpha ##
 
 #Typedef uint32_t SkPMColor
@@ -735,7 +735,7 @@
 
 #Method SkPMColor SkPreMultiplyARGB(U8CPU a, U8CPU r, U8CPU g, U8CPU b)
 #In Functions
-#Line # converts Unpremultiplied ARGB to Premultiplied PMColor ##
+#Line # converts Unpremultiplied ARGB to Premultiplied PM_Color ##
 
 Returns a SkPMColor value from Unpremultiplied 8-bit component values.
 
@@ -768,9 +768,9 @@
 
 #Method SkPMColor SkPreMultiplyColor(SkColor c)
 #In Functions
-#Line # converts Unpremultiplied Color to Premultiplied PMColor ##
+#Line # converts Unpremultiplied Color to Premultiplied PM_Color ##
 
-Returns PMColor closest to Color c. Multiplies c RGB components by the c Alpha,
+Returns PM_Color closest to Color c. Multiplies c RGB components by the c Alpha,
 and arranges the bytes to match the format of kN32_SkColorType.
 
 #Param c  Unpremultiplied ARGB Color  ##
@@ -800,6 +800,6 @@
 
 #Method ##
 
-#Subtopic PMColor ##
+#Subtopic PM_Color ##
 
 #Topic Color ##