Fix: ini parser: truncation of value name

Fix: ini parser: truncation of value name

clang 14 reports the following:

  ini-config/ini.cpp:88:16: warning: 'char* strncpy(char*, const char*, size_t)' output may be truncated copying 49 bytes from a string of length 199 [-Wstringop-truncation]
     88 |         strncpy(dest, src, size - 1);
        |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~

Indeed, a silent truncation of `name` occurs whenever it is longer than
prev_name (49 characters, excluding the terminator).

Report an error when this condition occurs.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I973bd27185e0130d8e4a452525d9277de45ba200