Installing libmysqlclient15-dev without uninstalling mysql-server-5.5

Question

I am trying to install Redmine. Unfortunately the mysql gem keeps me from doing so.

    /usr/bin/ruby1.8 extconf.rb
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lm... yes
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lz... yes
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lsocket... no
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lnsl... yes
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lmygcc... no
checking for mysql_query() in -lmysqlclient... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

So I tried

aptitude install libmysqlclient15-dev

as this is said to fix this problem. BUT

The following packages have unmet dependencies:
  mysql-server-5.5: Breaks: libmysqlclient-dev (< 5.5.17~) but 5.1.66-0+squeeze1 is to be installed.
The following actions will resolve these dependencies:

 Remove the following packages:
 1)     mysql-server
 2)     mysql-server-5.5

The MySQL server is used on live homepages. Uninstalling it is not an option. Is it possible to install redmine some other way or do I have to look for an other system?

Thank you for your help!