only create or set Token::mMacroName if necessary

[firewave]

like we do with Token::mOriginalName

[firewave]

before

61,862,106,779 (100.0%)  PROGRAM TOTALS
[...]
6,518,845,572 (10.54%)  build/token.cpp:Token::Match(Token const*, char const*, int) [/home/runner/work/cppcheck/cppcheck/cppcheck]
3,829,073,229 ( 6.19%)  ./malloc/./malloc/malloc.c:_int_malloc [/usr/lib/x86_64-linux-gnu/libc.so.6]
3,077,333,815 ( 4.97%)  ./malloc/./malloc/malloc.c:_int_free [/usr/lib/x86_64-linux-gnu/libc.so.6]
2,047,873,515 ( 3.31%)  build/library.cpp:Library::detectContainerInternal(Token const*, Library::DetectContainer, bool*, bool) const [/home/runner/work/cppcheck/cppcheck/cppcheck]
1,501,109,740 ( 2.43%)  ./malloc/./malloc/malloc.c:malloc [/usr/lib/x86_64-linux-gnu/libc.so.6]
1,497,752,596 ( 2.42%)  ./string/../sysdeps/x86_64/multiarch/memchr-avx2.S:__memchr_avx2 [/usr/lib/x86_64-linux-gnu/libc.so.6]
1,333,776,480 ( 2.16%)  ./string/../sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S:__memcmp_avx2_movbe [/usr/lib/x86_64-linux-gnu/libc.so.6]
  761,135,725 ( 1.23%)  ./malloc/./malloc/malloc.c:free [/usr/lib/x86_64-linux-gnu/libc.so.6]
[...]

after

61,553,406,468 (100.0%)  PROGRAM TOTALS
[...]
6,518,845,572 (10.59%)  build/token.cpp:Token::Match(Token const*, char const*, int) [/home/runner/work/cppcheck/cppcheck/cppcheck]
3,747,489,901 ( 6.09%)  ./malloc/./malloc/malloc.c:_int_malloc [/usr/lib/x86_64-linux-gnu/libc.so.6]
3,073,493,502 ( 4.99%)  ./malloc/./malloc/malloc.c:_int_free [/usr/lib/x86_64-linux-gnu/libc.so.6]
2,047,873,515 ( 3.33%)  build/library.cpp:Library::detectContainerInternal(Token const*, Library::DetectContainer, bool*, bool) const [/home/runner/work/cppcheck/cppcheck/cppcheck]
1,501,438,060 ( 2.44%)  ./malloc/./malloc/malloc.c:malloc [/usr/lib/x86_64-linux-gnu/libc.so.6]
1,498,016,716 ( 2.43%)  ./string/../sysdeps/x86_64/multiarch/memchr-avx2.S:__memchr_avx2 [/usr/lib/x86_64-linux-gnu/libc.so.6]
1,337,576,862 ( 2.17%)  ./string/../sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S:__memcmp_avx2_movbe [/usr/lib/x86_64-linux-gnu/libc.so.6]
  761,375,173 ( 1.24%)  ./malloc/./malloc/malloc.c:free [/usr/lib/x86_64-linux-gnu/libc.so.6]
[...]