StringUtils::FormatV: optimization: reduce default allocation size to 512 bytes as most formatted strings are small, replace malloc/realloc with simpler malloc/free
[win32] StringUtils::FormatV: use exact size on Win32 instead of doubling
Merge pull request #5041 from Karlson2k/FormatV_upd_01

StringUtils::FormatV: optimize, use exact size on Win32 instead of doubling