LdScript: using cppGetc() in wrong ways

[masatake]

In many areas, the parser assumes values returned from cppGetc() are in the range of unsigned char, [0, 0xff]. An overhaul is needed.

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Can I pass the value returned from cppGetc() to isspace directly? This question is applicable to ld-script and cxx.

Originally posted by @masatake in https://github.com/universal-ctags/ctags/pull/3444#discussion_r926929752

[masatake]

See https://github.com/universal-ctags/ctags/pull/3690/commits/2cab33c5b8cacd2aeedcf4f8af5fe13ea68a561b .

[masatake]

This can be applicable to asm.c

[masatake]

[yamato@dev64]~/var/ctags-github% cat /tmp/input.lds 
0""
[yamato@dev64]~/var/ctags-github%  ./ctags /tmp/input.lds
ctags: ./main/vstring.h:110: vStringPutImpl: Assertion `c >= 0 && c <= 0xff' failed.
ctags: ./main/vstring.h:110: parsing /tmp/input.lds:1 as LdScript
zsh: IOT instruction (core dumped)  ./ctags /tmp/input.lds