doc: add more performance items to go1.5.txt

Change-Id: Ia7a08bc855db87890d35b2a1667e245ce5ecf472
Reviewed-on: https://go-review.googlesource.com/8197Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go1.5.txt

@@ -54,10 +54,19 @@ cmd/trace: new command to view traces (https://golang.org/cl/3601)
 Performance:
 
 cmd/gc: optimize memclr of slices and arrays (https://golang.org/cl/2520)
+cmd/gc: transform closure calls to function calls (https://golang.org/cl/4050)
+cmd/gc: evaluate concrete == interface without allocating (https://golang.org/cl/2096)
 cmd/internal/gc: transitive inlining (https://golang.org/cl/5952)
 cmd/internal/gc: inline x := y.(*T) and x, ok := y.(*T) (https://golang.org/cl/7862)
+cmd/internal/gc, runtime: speed up some cases of _, ok := i.(T) (https://golang.org/cl/7697)
+cmd/internal/gc: speed up large string switches (https://golang.org/cl/7698)
+encoding/xml: avoid an allocation for tags without attributes (https://golang.org/cl/4160)
+image: many optimizations
+runtime: add ARM runtime.cmpstring and bytes.Compare (https://golang.org/cl/8010)
 sort: number of Sort performance optimizations (https://golang.org/cl/2100, https://golang.org/cl/2614, ...)
 strconv: optimize decimal to string conversion (https://golang.org/cl/2105)
+strconv: optimize float to string conversion (https://golang.org/cl/5600)
+sync: add active spinning to Mutex (https://golang.org/cl/5430)
 math/big: faster assembly kernels for amd64 and 386 (https://golang.org/cl/2503, https://golang.org/cl/2560)
 math/big: faster "pure Go" kernels for platforms w/o assembly kernels (https://golang.org/cl/2480)
 regexp: port RE2's bitstate backtracker to the regexp package (https://golang.org/cl/2153)