Fixed size buffers

[mazes-80]

First pass to eliminate fixed size buffers (4 done).

There is 3 others places in the code where it happens, but my fixes involves GString
As your comments say you removed all references to GString, I didn't wanted to push them in this first pass.

[wdlkmpx]

I don't want GString, it's a regression. I used fixed buffers to optimize performance for some old 1995 pcs,
In some cases it's not an issue, e.g: reporting of errors

I'm aware of g_strconcat and other functions

[mazes-80]

allocating may be a performance issue on some old hardware I agree, and fixed size buffer isn't that bad sometimes but the one in history.c really is an issue.

Can you be tell more about your aversion for GString, I don't really get why you don't want them.

[wdlkmpx]

I think it's about applying stuff in a conservative way

For example. when searching the history, the app does not expect you to type a whole Word document, thus the fixed buffer of 1024 bytes (it could be 2048)

Using that buffer in an intelligent way is better than allocating buffers hundreds of times.

[mazes-80]

The reason I began gtk3, is my old (0.9.2) version of gmrun producing "segfaults" any time I launch it.
I had a shell one-liner in the history way over the limit of the buffer.

[wdlkmpx]

These changes are ok I think, but searching the history requires you to type characters one by one, so you're going to type more than 512 or 1024 characters, it's about being reasonable

A buffer overflow cannot happen, the code prevents it by checking boundaries.

[mazes-80]

Ah, yes fgets, still it impose limit to the size of lines in the history file