runtime/cgo: make symbol naming consistent

The naming in this package is a disaster.
Make it all consistent.

Remove some 'static' from functions that will
be referred to from other files soon.

This CL is purely renames using global search and replace.

Submitting separately so that real changes will not
be drowned out by these renames in future CLs.

TBR=iant
CC=golang-dev
https://golang.org/cl/7416046
diff --git a/src/pkg/runtime/cgo/gcc_freebsd_386.c b/src/pkg/runtime/cgo/gcc_freebsd_386.c
index 5dae2bf..f22d47b 100644
--- a/src/pkg/runtime/cgo/gcc_freebsd_386.c
+++ b/src/pkg/runtime/cgo/gcc_freebsd_386.c
@@ -11,8 +11,8 @@
 
 static void* threadentry(void*);
 
-static void
-xinitcgo(G *g)
+void
+x_cgo_init(G *g)
 {
 	pthread_attr_t attr;
 	size_t size;
@@ -23,10 +23,10 @@
 	pthread_attr_destroy(&attr);
 }
 
-void (*initcgo)(G*) = xinitcgo;
+void (*_cgo_init)(G*) = x_cgo_init;
 
 void
-libcgo_sys_thread_start(ThreadStart *ts)
+_cgo_sys_thread_start(ThreadStart *ts)
 {
 	pthread_attr_t attr;
 	sigset_t ign, oset;
@@ -61,7 +61,7 @@
 	ts.g->stackbase = (uintptr)&ts;
 
 	/*
-	 * libcgo_sys_thread_start set stackguard to stack size;
+	 * _cgo_sys_thread_start set stackguard to stack size;
 	 * change to actual guard pointer.
 	 */
 	ts.g->stackguard = (uintptr)&ts - ts.g->stackguard + 4096;