Bug 1060283 part 1 - Rename IonSpew to JitSpew. r=h4writer

--HG--
rename : js/src/jit/IonSpewer.cpp => js/src/jit/JitSpewer.cpp
rename : js/src/jit/IonSpewer.h => js/src/jit/JitSpewer.h
extra : rebase_source : 87ff9b0726ece57555e896a15ed7268a3f1d69e6