Syntax errors resets the lexer right away

`DEF`, `REDEF`, etc disable EQUS expansion, and reading
macro or OPT arguments sets the lexer to raw mode.
Syntax errors resume normal parsing at the line's end,
but should resume normal tokenization even before that.

test/asm/syntax-error-lexer-mode.out

@@ -0,0 +1,3 @@
+x=1, y=2
+n=2
+q=2