cmd/compile: move more compiler specifics into compiler specific export section
Instead of indicating with each function signature if it has an inlineable
body, collect all functions in order and export function bodies with function
index in platform-specific section.
Moves this compiler specific information out of the platform-independent
export data section, and removes an int value for all functions w/o body.
Also simplifies the code a bit.
Change-Id: I8b2d7299dbe81f2706be49ecfb9d9f7da85fd854
Reviewed-on: https://go-review.googlesource.com/21939 Reviewed-by: Matthew Dempsky <mdempsky@google.com>