[bug] failed to handle a long tag line

[masatake]

If a tag line is too long, searching a tag fails.

$ cat /tmp/foo.tags 
!_TAG_FILE_FORMAT	2	/extended format; --format=1 will not append ;" to lines/;"	extras:pseudo
!_TAG_FILE_SORTED	1	/0=unsorted, 1=sorted, 2=foldcase/;"	extras:pseudo
!_TAG_OUTPUT_EXCMD	mixed	/number, pattern, mixed, or combineV2/;"	extras:pseudo
!_TAG_OUTPUT_FILESEP	slash	/slash or backslash/;"	extras:pseudo
!_TAG_OUTPUT_MODE	u-ctags	/u-ctags or e-ctags/;"	extras:pseudo
!_TAG_PROC_CWD	/home/yamato/spelunker/satellite/	//;"	extras:pseudo
Available value types	README.md	/^####  Available value types$/;"	kind:subsubsection	line:439	language:Markdown	scope:section:Foreman Maintain [![Ruby Tests](https://github.com/theforeman/foreman_maintain/actions/workflows/ruby_tests.yml/badge.svg)](https://github.com/theforeman/foreman_maintain/actions/workflows/ruby_tests.yml) <a href="https://codeclimate.com/github/theforeman/foreman_maintain"><img src="https://codeclimate.com/github/theforeman/foreman_maintain/badges/gpa.svg" /></a>""Bash completion	roles:def	end:453	sectionMarker:#
Base	definitions/procedures/service/base.rb	/^    class Base < ForemanMaintain::Procedure$/;"	kind:class	line:3	language:Ruby	scope:module:Procedures.Service	inherits:ForemanMaintain.Procedure	roles:def	end:35
Bash completion	README.md	/^## Bash completion$/;"	kind:section	line:418	language:Markdown	scope:chapter:Foreman Maintain [![Ruby Tests](https://github.com/theforeman/foreman_maintain/actions/workflows/ruby_tests.yml/badge.svg)](https://github.com/theforeman/foreman_maintain/actions/workflows/ruby_tests.yml) <a href="https://codeclimate.com/github/theforeman/foreman_maintain"><img src="https://codeclimate.com/github/theforeman/foreman_maintain/badges/gpa.svg" /></a>	roles:def	end:463	sectionMarker:#
$ readtags -t /tmp/foo.tags Base
$ readtags -t /tmp/foo.tags -Q '(eq? $name "Base")' -l
Base	definitions/procedures/service/base.rb	/^    class Base < ForemanMaintain::Procedure$/

findFirstNonMatchBefore uses a constant (#define JUMP_BACK 512) for rewinding the input stream.
A line longer than JUMP_BACK causes trouble.