When the ## operator concatenates two tokens to form a function-like macro
name (e.g. PREFIX_ ## kind → PREFIX_SCALAR), simplecpp looked for the
argument list '(...)' only at B->next. In PAR-style indirection patterns
the '(' is separated from B by a comma or a variadic parameter token:

#define PAR(a, ...) a VA_ARGS
#define PREFIX_SCALAR(T, N) T N
#define DISPATCH(kind, ...) PAR(PREFIX_ ## kind, (VA_ARGS))
DISPATCH(SCALAR, int, x) // was: [unknownMacro] — now: int x

Because '(' was not found, expansion was aborted and the macro was
reported as unknownMacro, causing cppcheck to skip the entire translation
unit.

Fix: when B->next is not '(' and we are in the appendTokens context
(expandResult==false), walk forward on the same line skipping ',' separators
and resolving named parameter tokens via expandArg(). The first '(' found
(literally or as the head of an expanded argument) is used as lpar and
passed to appendTokens() as before. The forwardScan flag ensures
expandToken() is called on the result even when expandResult is false.

The forward scan is restricted to expandResult==false to avoid unintended
side-effects in the main expansion loop.

Add test preprocessor_doublesharp_funclike_forward_scan covering:

• single DISPATCH call (PAR pattern with VA_ARGS indirection)
• chained calls with two different PREFIX_ specialisations