isLexVarSym: check all characters of the name, not just the first one.
isLexVarSym: check all characters of the name, not just the first one.

This is so that generated names like e.g. workers don't show up as
infix operators when using something like -ddump-simpl.

(cherry picked from commit a3f78e2476e3d4ead86ef3b10ddd4e14e189ada3)

hferreiro/replay,lukexi/ghc-7.8-arm64,hferreiro/replay,lukexi/ghc-7.8-arm64,hferreiro/replay,hferreiro/replay,lukexi/ghc-7.8-arm64,lukexi/ghc-7.8-arm64,hferreiro/replay,hferreiro/replay,lukexi/ghc-7.8-arm64,hferreiro/replay