suppress "Separator in survey name" warning

[speleo3]

Current survex allows introducing survey name "a.b" implicitly and then entering "a" and "b" one after the other without any warnings:

; no warnings
1       2       1.0     0.0     0.0
2       a.b.1   1.0     90.0    0.0
*begin a
*begin b
1       2       1.0     180.0   0.0
*end b
*end a

However, entering "a.b" directly gives a warning:

; warning: Separator in survey name
1       2       1.0     0.0     0.0
2       a.b.1   1.0     90.0    0.0
*begin a.b
1       2       1.0     180.0   0.0
*end a.b

I see no reason why syntax 2 should be discouraged. This PR suppresses the warning.

[ojwb]

I'm not really sold on this change. There is a difference between the two cases - in the first case there's an actual definition of survey a (albeit one which only contains the definition of a sub-survey), whereas in the second case a is never actually defined anywhere.

I think the underlying problem here (as it was in #4) is that you want to be able to essentially freely use . as a character in survey station names, but Survex by default interprets . as separating levels in the survey hierarchy, and complains based on that interpretation.

And as with #4, I think the better answer if you want to use . freely is to set a different character as the survey hierarchy level separator and add . to the characters allowed in a name.

[waldekgraban]

In fact, the option to solve the problem without interfering with the code is probably always the best.