Parser: various mixings of attributes/alignas are not accepted, but should be

[davmac314]

Describe the bug
Various mixings of [[attr]]-style and __attribute__((attr)) attributes, and the alignas(n) specifier, should be accepted by the parser, but are rejected (highlighted with yellow underline and "syntax error" alert).

To Reproduce

int v1 alignas(16); // should be ok but rejected
alignas(16) int v2; // (ok)
int v3 [[maybe_unused]] __attribute__((section(".foo"))) [[maybe_unused]] __attribute__((section(".foo"))); // (ok)
[[maybe_unused]] __attribute__((section(".foo"))) int v5; // (ok)
__attribute__((section(".foo"))) [[maybe_unused]] int v5; // (ok)
[[maybe_unused]] __attribute__((section(".foo")))
        [[maybe_unused]] __attribute__((section(".foo"))) int v4; // should be ok but rejected
alignas(16) __attribute__((section(".foo"))) [[maybe_unused]] int v5; // should be ok but rejected
alignas(16) [[maybe_unused]] __attribute__((section(".foo"))) int v6; // (ok)

Expected behavior
All lines above should be accepted by the parser

Version Information (please complete the following information):

• OS: Linux
• Eclipse Version: 2025-06 (4.36)
• CDT Version: 12.1.0.202506041907