cgen: remove more things from c_reserved

[dy-tea]

Describe the feature

This list of keywords is defined in vlib/v/gen/c/cgen.v.

Since we prefix the builtin functions with builtin__, many of these keywords should not appear in generated C code.

Use Case

This will both simplify cgen and make some bugs less likely. I was encountering an issue where I wanted to get a field link from a struct in comptime but link was being replaced with __v_link, meaning invalid C code was generated. For link specifically I could not find where this was reserved unlike some of the reserved words defined by microsoft in headers or similar.

Proposed Solution

Ascertain which keywords may still be needed and remove the rest.

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

Version used

V 0.5.0 a3fd7f3

Environment details (OS name and version, etc.)

V full version	V 0.5.0 ba97785.a3fd7f3
OS	linux, "CachyOS"
Processor	12 cpus, 64bit, little endian, 13th Gen Intel(R) Core(TM) i5-1335U
Memory	5.26GB/15.31GB
V executable	/home/dylan/Repos/v/v
V last modified time	2025-12-31 22:26:05
V home dir	OK, value: /home/dylan/Repos/v
VMODULES	OK, value: /home/dylan/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/dylan
Git version	git version 2.52.0
V git status	0.5-1-ga3fd7f39
.git/config present	true
cc version	cc (GCC) 15.2.1 20251112
gcc version	gcc (GCC) 15.2.1 20251112
clang version	clang version 21.1.6
tcc version	tcc version 0.9.28rc 2025-02-13 HEAD@f8bd136d (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 696c1d84
emcc version	N/A
glibc version	ldd (GNU libc) 2.42

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