Add support for files with multiline macros

[milasudril]

C++ scanner fails on this:

#define IDIS_INCBIN(identifier, filename) \
asm(".pushsection .rodata\n" \
        "\t.local " #identifier "_begin\n" \
        "\t.type " #identifier "_begin, @object\n" \
        "\t.align 16\n" \
        #identifier "_begin:\n" \
        "\t.incbin \"" filename "\"\n\n" \
\
        "\t.local " #identifier "_end\n" \
        "\t.type " #identifier "_end, @object\n" \
        "\t.align 1\n" \
        #identifier "_end:\n" \
        "\t.byte 0\n" \
        "\t.popsection\n"); \
\
extern std::byte const identifier ## _begin[];\
extern std::byte const identifier ## _end[]

It thinks #identifier is another include.