Fix #1631 - Disable balloon support for terminals by default

doc/ale.txt

@@ -1401,8 +1401,7 @@ g:ale_set_balloons                                         *g:ale_set_balloons*
                                                            *b:ale_set_balloons*
 
   Type: |Number|
-  Default: `(has('balloon_eval') && has('gui_running'))`
-           `|| (has('balloon_eval_term') && !has('gui_running'))`
+  Default: `has('balloon_eval') && has('gui_running')`
 
   When this option is set to `1`, balloon messages will be displayed for
   problems or hover information if available.
@@ -1412,6 +1411,12 @@ g:ale_set_balloons                                         *g:ale_set_balloons*
   supporting "Hover" information, per |ale-hover|, then brief information
   about the symbol under the cursor will be displayed in a balloon.
 
+  Balloons can be enabled for terminal versions of Vim that support balloons,
+  but some versions of Vim will produce strange mouse behavior when balloons
+  are enabled. To configure balloons for your terminal, you should first
+  configure your |ttymouse| setting, and then consider setting
+  `g:ale_set_balloons` to `1` before ALE is loaded.
+
   `b:ale_set_balloons` can be set to `0` to disable balloons for a buffer.
   Balloons cannot be enabled for a specific buffer when not initially enabled
   globally.

plugin/ale.vim

@@ -108,10 +108,7 @@ let g:ale_set_highlights = get(g:, 'ale_set_highlights', has('syntax'))
 let g:ale_echo_cursor = get(g:, 'ale_echo_cursor', 1)
 
 " This flag can be set to 0 to disable balloon support.
-let g:ale_set_balloons = get(g:, 'ale_set_balloons',
-\   (has('balloon_eval') && has('gui_running'))
-\   || (has('balloon_eval_term') && !has('gui_running'))
-\)
+let g:ale_set_balloons = get(g:, 'ale_set_balloons', has('balloon_eval') && has('gui_running'))
 
 " This flag can be set to 0 to disable warnings for trailing whitespace
 let g:ale_warn_about_trailing_whitespace = get(g:, 'ale_warn_about_trailing_whitespace', 1)