Full support of English documents

Fix functions relating YaTeX-beginning-of-environment or ...

YaTeX-end-of-environment.
Line indentation by TAB much improved.
Functions that work at enclosing environments, YaTeX-enclose-<ENVNAME>,
introduced.  Functions for enclosing verbatim and equations are supplied.
SPC, DEL, +, - in YaTeX-hierarchy buffer.
Compensate odd highlighting of hilit19.

Set YaTeX-indent-line to 'indent-line-function. ...

Revise fill features.

Created `ChangeLog'. ...

Log hereafter will be written in `ChangeLog'.

Abolish user-article table. ...

Use normal read-string instead.
Supply smart add-in function for documentstyle.
Update user dictionary whenever new words entered.
Enhance [prefix] c.
Allow user defined sectioning commands in yatexsec.

Support special popup frame. ...

Refine highlightening method.
On Emacs-19, couldn't save user completion table correctly, fixed.

Support Mule2

Change the YaTeX-math-mode's prefix from `,' to `;'. ...

Add YaTeX-apropos, YaTeX-what-column, YaTeX-beginning-of-environment,
YaTeX-end-of-environment.
Add variables YaTeX-default-pop-window-height, YaTeX-close-paren-always,
YaTeX-no-begend-shortcut, YaTeX-auto-math-mode.
Remove Greek letters from maketitle-type.
Make YaTeX-inner-environment two times faster and more reliable.
C-u for [prefix] k kills contents too.
Fix the detection of the range of section-type commands when nested.
Add \end{ completion.
Add YaTeX-generate-simple.
Refine documents(using Texinfo).
%#REQUIRE for sub-preambles.