Update README.txt (#4368)

* Update README.txt

As of Ubuntu 16.10, libpng12-dev is replaced with libpng12-0, since libpng12-0 is available in 16.04 repositories, I think that needed to be changed.

Also I changed 'git-core' to 'git' for fedora users, keep it consistent with the ubuntu/debian instructions.

* Update README.txt

README.txt

@@ -103,7 +103,7 @@ Compiling on GNU/Linux:
 -----------------------
 
 Install dependencies. Here's an example for Debian/Ubuntu:
-$ sudo apt-get install build-essential libirrlicht-dev cmake libbz2-dev libpng12-dev libjpeg-dev libxxf86vm-dev libgl1-mesa-dev libsqlite3-dev libogg-dev libvorbis-dev libopenal-dev libcurl4-gnutls-dev libfreetype6-dev zlib1g-dev libgmp-dev libjsoncpp-dev
+$ sudo apt-get install build-essential libirrlicht-dev cmake libbz2-dev libpng-dev libjpeg-dev libxxf86vm-dev libgl1-mesa-dev libsqlite3-dev libogg-dev libvorbis-dev libopenal-dev libcurl4-gnutls-dev libfreetype6-dev zlib1g-dev libgmp-dev libjsoncpp-dev
 
 For Fedora users:
 $ sudo dnf install make automake gcc gcc-c++ kernel-devel cmake libcurl* openal* libvorbis* libXxf86vm-devel libogg-devel freetype-devel mesa-libGL-devel zlib-devel jsoncpp-devel irrlicht-devel bzip2-libs gmp-devel sqlite-devel luajit-devel leveldb-devel ncurses-devel doxygen spatialindex-devel bzip2-devel
@@ -114,7 +114,7 @@ This is an example for installing git on Debian/Ubuntu:
 $ sudo apt-get install git
 
 For Fedora users:
-$ sudo dnf install git-core
+$ sudo dnf install git
 
 Download source (this is the URL to the latest of source repository, which might not work at all times) using git:
 $ git clone --depth 1 https://github.com/minetest/minetest.git