libgmp3-dev is already the newest version (2:6.1.2+dfsg-1).
libxml2-dev is already the newest version (2.9.4+dfsg1-2.2+deb9u2).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
root@vmi252307:~/ots/source# libxml2-dev
-bash: libxml2-dev: command not found
root@vmi252307:~/ots/source# apt-get --purge remove libxml2-dev; apt-get install libxml-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libglib2.0-bin libglib2.0-dev libglibmm-2.4-1v5 libglibmm-2.4-dev
  libpcre16-3 libpcre3-dev libpcre32-3 libpcrecpp0v5 libsigc++-2.0-0v5
  libsigc++-2.0-dev libxml++2.6-2v5
Use 'apt autoremove' to remove them.
The following packages will be REMOVED:
  libxml++2.6-dev* libxml2-dev*
0 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
After this operation, 4,174 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 52847 files and directories currently installed.)
Removing libxml++2.6-dev:amd64 (2.40.1-1) ...
Removing libxml2-dev:amd64 (2.9.4+dfsg1-2.2+deb9u2) ...
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package libxml-dev
root@vmi252307:~/ots/source# apt-get install [COLOR=#333333]zlib1g-dev zlib1g[/COLOR]
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package [COLOR
E: Couldn't find any package by glob '[COLOR'
E: Regex compilation error - Unmatched [ or [^
E: Couldn't find any package by regex '[COLOR'
E: Unable to locate package zlib1g[
E: Couldn't find any package by glob 'zlib1g['
E: Regex compilation error - Invalid regular expression
E: Couldn't find any package by regex 'zlib1g['
root@vmi252307:~/ots/source# apt-get install zlib1g-dev zlib1g libxml++2.6-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
zlib1g is already the newest version (1:1.2.8.dfsg-5).
zlib1g-dev is already the newest version (1:1.2.8.dfsg-5).
zlib1g-dev set to manually installed.
The following additional packages will be installed:
  libxml2-dev
Suggested packages:
  libxml++2.6-doc
The following NEW packages will be installed:
  libxml++2.6-dev libxml2-dev
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 927 kB of archives.
After this operation, 4,174 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://asi-fs-n.contabo.net/debian stretch/main amd64 libxml2-dev amd64 2.9.4+dfsg1-2.2+deb9u2 [812 kB]
Get:2 http://asi-fs-n.contabo.net/debian stretch/main amd64 libxml++2.6-dev amd64 2.40.1-1 [116 kB]
Fetched 927 kB in 0s (41.7 MB/s)
Selecting previously unselected package libxml2-dev:amd64.
(Reading database ... 52721 files and directories currently installed.)
Preparing to unpack .../libxml2-dev_2.9.4+dfsg1-2.2+deb9u2_amd64.deb ...
Unpacking libxml2-dev:amd64 (2.9.4+dfsg1-2.2+deb9u2) ...
Selecting previously unselected package libxml++2.6-dev:amd64.
Preparing to unpack .../libxml++2.6-dev_2.40.1-1_amd64.deb ...
Unpacking libxml++2.6-dev:amd64 (2.40.1-1) ...
Setting up libxml2-dev:amd64 (2.9.4+dfsg1-2.2+deb9u2) ...
Setting up libxml++2.6-dev:amd64 (2.40.1-1) ...
root@vmi252307:~/ots/source# sed -i 's/  -lxml2$/ -lxml2 -lpthread/' Makefile
root@vmi252307:~/ots/source# make
make  all-am
make[1]: Entering directory '/root/ots/source'
g++ -DHAVE_CONFIG_H -I.    -I/usr/include/libxml2  -I/usr/include/lua5.1  -D__USE_MYSQL__     -D__ENABLE_SERVER_DIAGNOSTIC__ -D_THREAD_SAFE -D_REENTRANT -Wall -g -O1 -MT game.o -MD -MP -MF .deps/game.Tpo -c -o game.o game.cpp
game.cpp: In member function ‘Item* Game::findItemOfType(Cylinder*, uint16_t, bool, int32_t)’:
game.cpp:1659:10: error: cannot convert ‘bool’ to ‘Item*’ in return
   return false;
          ^~~~~
Makefile:564: recipe for target 'game.o' failed
make[1]: *** [game.o] Error 1
make[1]: Leaving directory '/root/ots/source'
Makefile:416: recipe for target 'all' failed
make: *** [all] Error 2