Warnings due to multiple "sectioning" commands inside an \if type construct

[albert-github]

When having a construct like:

/*!
@if LANG_ENGLISH
@file test.h

This is the description of test.h

@class Dtk::Core::Fn_Test test.h
@brief Fn_Test class.

Details about Fn_Test.

@fn const char *Fn_Test::member(char c,int n)
@brief A member function.

Details of the function

@param c a character.
@param n an integer.
@exception std::out_of_range parameter is out of range.
@return a character pointer.

@fn void Fn_Test::undocumented()
@brief test

@endif
*/

we get warnings like:

.../test.en_US.dox:7: warning: Documentation block ended in the middle of a conditional section!
.../test.en_US.dox:25: warning: found \endif without matching start command

due to the fact that the part about the \file is ended by means of the \class command and later restarted but the test about the \if termination does not know about this restart (and thus the warning), and when restarted the \if... stack is newly defined specified so the \endif is on its own.

We need to "save" the stack for further use.

Example: example.tar.gz