Fix documentation

Restores erroneous changes to lexicon_filter and changes to doc_src/ pages. Done by hand to ensure version history.

Fixes display of % when misinterpreted by Doxygen.

doc_src/index.hdr.in

@@ -70,7 +70,7 @@ rm "cumbersome filename.txt"
 Will remove the file 'cumbersome filename.txt', while
 
 \fish
-rm \asis{cumbersome filename.txt}
+rm <asis>cumbersome filename.txt</asis>
 \endfish
 
 would remove the two files 'cumbersome' and 'filename.txt'.
@@ -553,22 +553,22 @@ Lists adjacent to other lists or strings are expanded as cartesian products:
 Examples:
 \fish{cli-dark}
 >_ echo {good,bad}" apples"
-\outp{good apples bad apples}
+<outp>good apples bad apples</outp>
 
 >_ set -l a x y z
 >_ set -l b 1 2 3
 
 >_ echo $a$b
-\outp{x1 y1 z1 x2 y2 z2 x3 y3 z3}
+<outp>x1 y1 z1 x2 y2 z2 x3 y3 z3</outp>
 
 >_ echo $a"-"$b
-\outp{x-1 y-1 z-1 x-2 y-2 z-2 x-3 y-3 z-3}
+<outp>x-1 y-1 z-1 x-2 y-2 z-2 x-3 y-3 z-3</outp>
 
 >_ echo {x,y,z}$b
-\outp{x1 y1 z1 x2 y2 z2 x3 y3 z3}
+<outp>x1 y1 z1 x2 y2 z2 x3 y3 z3</outp>
 
 >_ echo {$b}word
-\outp{1word 2word 3word}
+<outp>1word 2word 3word</outp>
 \endfish
 
 Be careful when you try to use braces to separate variable names from text. The dangers noted in the last example above can be avoided by wrapping the variable in double quotes instead of braces (`echo "$b"word`).
@@ -639,7 +639,7 @@ This form of expansion is useful for commands like kill and fg, which take proce
 
 Example:
 
-`fg %ema` will search for a process whose command line begins with the letters 'ema', such as emacs, and if found, put it in the foreground.
+`fg %%ema` will search for a process whose command line begins with the letters 'ema', such as emacs, and if found, put it in the foreground.
 
 `kill -s SIGINT %3` will send the SIGINT signal to the job with job ID 3.