runtime: initialize hash algs before typemap

When compiling with -buildmode=shared, a map[int32]*_type is created for
each extra module mapping duplicate types back to a canonical object.
This is done in the function typelinksinit, which is called before the
init function that sets up the hash functions for the map
implementation. The result is typemap becomes unusable after
runtime initialization.

The fix in this CL is to move algorithm init before typelinksinit in
the runtime setup process. (For 1.8, we may want to turn typemap into
a sorted slice of types and use binary search.)

Manually tested on GOOS=linux with:

	GOHOSTARCH=386 GOARCH=386 ./make.bash && \
		go install -buildmode=shared std && \
		cd ../test && \
		go run run.go -linkshared

Fixes #16590

Change-Id: Idc08c50cc70d20028276fbf564509d2cd5405210
Reviewed-on: https://go-review.googlesource.com/25469
Run-TryBot: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/runtime/alg.go

@@ -289,7 +289,7 @@ var aeskeysched [hashRandomBytes]byte
 // used in hash{32,64}.go to seed the hash function
 var hashkey [4]uintptr
 
-func init() {
+func alginit() {
 	// Install aes hash algorithm if we have the instructions we need
 	if (GOARCH == "386" || GOARCH == "amd64") &&
 		GOOS != "nacl" &&

src/runtime/proc.go

@@ -439,7 +439,8 @@ func schedinit() {
 	stackinit()
 	mallocinit()
 	mcommoninit(_g_.m)
-	typelinksinit()
+	alginit()       // maps must not be used before this call
+	typelinksinit() // uses maps
 	itabsinit()
 
 	msigsave(_g_.m)