With read_file() revamped, it now uses partition_filestruct() indirectly
via ingraft_buffer(), so we can't use partition_filestruct() to replace
marked text in the alternate spell checker anymore without segfaulting.

Add the new function replace_marked_buffer() to accomplish this instead.
Based on replace_buffer(), it uses extract_buffer() to throw away the
marked un-spell-checked text, and then uses read_file() to insert the
spell-checked text at the position where the mark was.

Accordingly, remove unneeded partitioning and related stuff from
do_alt_speller().  Besides pasting the file into the buffer at
current[current_x], ingraft_buffer() also deals with renumbering,
updating totsize, and handling a magicline, so do_alt_speller()
doesn't need to do those anymore.

With read_file() revamped to handle inserting a file at the current
position, partitioning the buffer is no longer needed.

Move buffer handling and '\r' stripping from read_line() to read_file(),
so that the file gets its format determined and gets stored in its own
buffer entirely in one function.  Then use ingraft_buffer() to insert
this new buffer into the current one.

In addition to pasting the file at current[current_x], ingraft_buffer()
also deals with renumbering, the updating of totsize, and the handling
of a magicline, so read_file() doesn't need to do those anymore.

Note that all this makes read_file() depend on the position of
current[current_x] to know where to insert the file.  Accordingly,
set current_x to zero in initialize_buffer_text() instead of in
make_new_buffer(), so that replace_buffer() keeps working properly.

Also, avoid a warning with with --enable-tiny --enable-browser.

Of course 'row' needs to be initialized to zero for the softwrap case.

This addresses https://savannah.gnu.org/patch/?9215

.
Inspired-by: David Lawrence Ramsey <pooka109@gmail.com>

Add its explanation as a separate paragraph.

Also: improve the argument of the --syntax option, as this is a <name>
and not merely a bundle of characters like the other <str> arguments.

In this last loop of break_line(), the pointer 'line' is one step ahead
of the index 'lastblank'.  So the loop should first add the length of
the preceding character to 'lastblank' before determining the length
of the current character (and using this to advance 'line').

(There is something wrong in the last loop: line is one character ahead
of lastblank, but the current character length is added to both of them.
It thus assumes that all blank characters are the same number of bytes.
For spaces and tabs this works fine.  But for more exotic blanks...)

Also, remove an assert and adjust some comments.

Also, rename a parameter to be less cryptic, and remove an entire
condition because the relevant block will never be reached when
getting called from the help routines: if blank_loc is negative,
the function will have bailed out in the preceding if.

In softwrap mode, the entire line is onscreen, so the word is never
partially offscreen, so we always have enough columns to show it.

This fixes https://savannah.gnu.org/bugs/?50389

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Reported-by: David Lawrence Ramsey <pooka109@gmail.com>

Give the strlenpt() routine its own implementation, so that it avoids
a needless comparison plus subtraction in the inner loop.

Instead of allocating enough space to convert the entire passed string,
just allocate space for converting the part that will be converted --
that is: starting from start_index.  This still allocates far too much
(if the passed string is very long and its tail part won't fit on the
screen), but it's better than before.

This fixes https://savannah.gnu.org/bugs/?50379.

Cap the number of pauses when displaying ALERT messages, to avoid
making the user wait for ages when tens or hundreds of files were
specified on the command line.

This fixes https://savannah.gnu.org/bugs/?50362

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Reported-by: Mike Frysinger <vapier@gentoo.org>

Reflect the significant changes in painting and regex searching
in the copyright notices.

Later on we're going to need the ability to graft a buffer into the
current file buffer without making a copy of it first.

The name "filestruct" was a mistake.  What was meant was:
buffer -- a linked list of structs that each describe a line.

When in softwrap mode, no "$" continuation characters are displayed,
so the code that reserves space for them should be skipped then.

This fixes https://savannah.gnu.org/bugs/?50335.

As a small service to the user, reject empty regex strings,
because an entirely empty regex simply doesn't make sense.
Inspired-by: Elia Geretto <elia.f.geretto@gmail.com>

When the marked region covers only a single line (or a part of it),
its new endpoint is not simply the length of the last line of the
spell-checked text, but instead the old endpoint plus the /change/
in length.

This fixes https://savannah.gnu.org/bugs/?50316

.
Reported-by: David Lawrence Ramsey <pooka109@gmail.com>

The inversion of the logic in commit a6605dce was incomplete -- oops.

This fixes https://savannah.gnu.org/bugs/?50306.

The previous code only directly refreshed the screen when the margin
changed due to toggling line numbering on.  When the margin changed
due to toggling it off, it would indirectly refresh via do_toggle().