runtime(java): Tidy up the documentation for "ft-java-syntax"

- Reword a few sentences and reformat a few paragraphs.
- Supply absent capitalisation and punctuation.
- Make listed highlighting groups and code stand out.
- Prefix all Java-related global variables with "g:".
- Add spaces around each variable assignment operator.
- Acknowledge that some Javadoc variables are maintained in
  the HTML syntax file.

Also, move the overridable _default_ HTML group links before
the HTML syntax file inclusion in order to implement the
documented diverged settings.

related: #15399

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/java.vim b/runtime/syntax/java.vim
index 9c4964d..a63ae02 100644
--- a/runtime/syntax/java.vim
+++ b/runtime/syntax/java.vim
@@ -3,7 +3,7 @@
 " Maintainer:		Aliaksei Budavei <0x000c70 AT gmail DOT com>
 " Former Maintainer:	Claudio Fleiner <claudio@fleiner.com>
 " Repository:		https://github.com/zzzyxwvut/java-vim.git
-" Last Change:		2024 Jul 23
+" Last Change:		2024 Jul 30
 
 " Please check :help java.vim for comments on some of the options available.
 
@@ -309,6 +309,12 @@
 hi def link javaCommentStart javaComment
 
 if !exists("java_ignore_javadoc") && main_syntax != 'jsp'
+  " The overridable "html*" default links must be defined _before_ the
+  " inclusion of the same default links from "html.vim".
+  hi def link htmlComment	Special
+  hi def link htmlCommentPart	Special
+  hi def link htmlArg		Type
+  hi def link htmlString	String
   syntax case ignore
 
   " Include HTML syntax coloring for Javadoc comments.
@@ -601,10 +607,6 @@
 hi def link javaType			Type
 hi def link javaExternal		Include
 
-hi def link htmlComment		Special
-hi def link htmlCommentPart		Special
-hi def link htmlArg			Type
-hi def link htmlString			String
 hi def link javaSpaceError		Error
 
 if s:module_info_cur_buf
diff --git a/runtime/syntax/testdir/dumps/java_comments_02.dump b/runtime/syntax/testdir/dumps/java_comments_02.dump
index 008a3e0..25babc7 100644
--- a/runtime/syntax/testdir/dumps/java_comments_02.dump
+++ b/runtime/syntax/testdir/dumps/java_comments_02.dump
@@ -1,7 +1,7 @@
 | +0#0000e05#ffffff0@3|*| |@+0#e000e06&|r|e|t|u|r|n| +0#0000e05&|{+0#e000e06&|@|c|o|d|e| |n|u|l@1|}| +0#0000e05&|*|/| +0#0000000&@45
 @4|V|o|i|d| |n|o|O|p|4|(|)| |{| |r+0#af5f00255&|e|t|u|r|n| +0#0000000&|n+0#e000002&|u|l@1|;+0#0000000&| |}| @41
 @75
-@4|/+0#0000e05&|*@1| +0#e000e06&|N|o|-|o|p|,| |i|.|e|.|<+0#0000e05&|!|-@1| |-@1|>| +0#e000e06&|n|o| |o|p|e|r|a|t|i|o|n|.| +0#0000000&@33
+@4|/+0#0000e05&|*@1| +0#e000e06&|N|o|-|o|p|,| |i|.|e|.|<|!|-@1| |-@1|>| |n|o| |o|p|e|r|a|t|i|o|n|.| +0#0000000&@33
 | +0#0000e05&@3|*| |@+0#e000e06&|r|e|t|u|r|n| +0#0000e05&|{+0#e000e06&|@|c|o|d|e| |n|u|l@1|}| +0#0000e05&|*|/| +0#0000000&@45
 @4>V|o|i|d| |n|o|O|p|5|(|)| |{| |r+0#af5f00255&|e|t|u|r|n| +0#0000000&|n+0#e000002&|u|l@1|;+0#0000000&| |}| @41
 @75