Fixed bug that causes parsing of the string "$x{" to fail.

Before the lexer would lex the line

echo "$x{";

into the tokens

QUOTE ("), T_VARIABLE ($x), T_ENCAPSED_AND_WHITESPACE ({";)

whereas it should do something in the lines of

QUOTE ("), T_VARIABLE ($x), T_ENCAPSED_AND_WHITESPACE ({), QUOTE ("), T_SEMICOLON (;)