syscall: Convert textflags from numbers to symbols.

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/12773043
math: convert textflags from numbers to symbols

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/12773044
all: change textflags from numbers to symbols.

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/12774043