compiler: inline call expressions and function references

Scan inlinable methods for references to global variables and
functions (forgot to do that earlier).

Track all packages mentioned by exports (that should have been done
earlier too).

Record assembler name in export data, so that we can inline calls to
non-Go functions.  Modify gccgoimporter code to skip assembler name.

This increases the number of inlinable functions in the standard
library from 215 to 439.

Change-Id: Ia69dea4ba99e0f1dfb9e3bf072feb95b1edaccb0
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/180677
Reviewed-by: Cherry Zhang <cherryyz@google.com>
7 files changed