runtime: paste mprof.goc into mprof.go as comments

NO CODE CHANGES HERE

The first conversion was not complete.
This CL doesn't make any actual changes,
but it inserts the missing mprof.goc code
as comments so that the next CL will have
useful diffs.

To make the diffs a bit more useful, removed
all semicolons, ->, and runtime· prefixes as well.

Also corrected order of a few functions in mprof.go
to match original order in mprof.goc.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews, iant, khr, r
https://golang.org/cl/134200043