bug#73484: 31.0.50; Abolishing etags-regen-file-extensions

["Francesco Potortì" <pot@gnu.org>]

Eli Zaretskii:
>> How hard is it to add to a live TAGS file fake lines which look like
>> this:
>> 
>>    ^L
>>    foo,0
>> 
>> (with random strings instead of "foo"), and then time some TAGS-using
>> commands with and without these additions?

Dmitry Gutov:
>Okay, done that.
>
>'M-.' takes more or less the same.
>
>The file size of TAGS increased from 66 MB to 85 MiB.
>
>Won't measure time to generate now - because the current method and the 
>"real" one will be different, but note that it's more relevant with 
>etags-regen-mode because the scan is performed lazily: every time the 
>user does the first search in a new project.

Removing the Fortran and C/C++ fallbacks just for testing requires recompiling etags.c after removing the code beginning with /* Else try Fortran or C. */.  This would avoid parsing the file (except for detecting the sharp-bang) and would leave the file name in the tags file, without tags.