In case in fixed format code a line like:
"     x   ( " existed and the x was on position 6 the "x   (" was seen as the start of a function call.

Fix bug: language switch command skipped when langauge id contains "-" letter

Fixed typos in comments.

Support language switch for language ids, 'Japanese-en', 'Korean-en', 'Serbian-Cyrillic', and similer langauge ids.

Support visible=no for main page tab.

Bug ?? for page numbers in the latex indices

LaTeX problem with 2 consecutive single quotes

Due to the fact that the path was not stripped from the file name in case CREATE_SUBDIRS was set to YES there was a reference to a non existing page reference. In the corresponding hypertarget and label the path was already stripped.

In LaTeX 2 consecutive single quotes are joined to 1 double quote. This leads in texts where 2 single quotes are intended to a strange view. An example is the initial value for variables. E.g. in Fortran: character(len=10) :: A = ''  (i.e an empty string which can either be defined as '' or as "") or in C: char *sq  = "''". In the source listings this is OK but in the description text it was not OK.