This permits an atomic check for error conditions and helps avoid
inconsistency between check and use of file name, which can also
pose security issues (not in the previous code, as the check was only
used for error-reporting).
Detected by Coverty scan, CID 185400
As it seems, different C compilers have different rules/interpretations
on inline functions. The current code base did not properly obey all C99
rules. We fix this by converting some functions to macros and others to
include the necessary C99 plumbing. We also remove some inline attributes
for functions where this seems to be to agressive (aka "function to big").
This fixes build problems in some environments and is a general code
cleanup measure.
