[Docs] Another round of stylistic fixes.

docs/linux_building_debug_gtk.md

-# Introduction
+# Linux — Building and Debugging GTK
 
 Sometimes installing the debug packages for gtk and glib isn't quite enough.
 (For instance, if the artifacts from -O2 are driving you bonkers in gdb, you
 might want to rebuild with -O0.)
-Here's how to build from source and use your local version without installing it.
+Here's how to build from source and use your local version without installing
+it.
+
+[TOC]
 
 ## 32-bit systems
 
 On Ubuntu, to download and build glib and gtk suitable for debugging:
 
-1. If you don't have a gpg key yet, generate one with gpg --gen-key.
+1.  If you don't have a gpg key yet, generate one with `gpg --gen-key`.
+2.  Create file `~/.devscripts` containing `DEBSIGN_KEYID=yourkey`, e.g.
+    `DEBSIGN_KEYID=CC91A262` (See
+    http://www.debian.org/doc/maint-guide/ch-build.en.html)
+3.  If you're on a 32 bit system, do:
 
-2. Create file ~/.devscripts containing DEBSIGN\_KEYID=yourkey, e.g.
-DEBSIGN\_KEYID=CC91A262
-(See http://www.debian.org/doc/maint-guide/ch-build.en.html
+    ```shell
+    #!/bin/sh
+    set -x
+    set -e
+    # Workaround for "E: Build-dependencies for glib2.0 could not be satisfied"
+    # See also https://bugs.launchpad.net/ubuntu/+source/apt/+bug/245068
+    sudo apt-get install libgamin-dev
+    sudo apt-get build-dep glib2.0 gtk+2.0
+    rm -rf ~/mylibs
+    mkdir ~/mylibs
+    cd ~/mylibs
+    apt-get source glib2.0 gtk+2.0
+    cd glib2.0*
+    DEB_BUILD_OPTIONS="nostrip noopt debug" debuild
+    cd ../gtk+2.0*
+    DEB_BUILD_OPTIONS="nostrip noopt debug" debuild
+    ```
 
-3. If you're on a 32 bit system, do:
-```
-#!/bin/sh
-set -x
-set -e
-# Workaround for "E: Build-dependencies for glib2.0 could not be satisfied"
-# See also https://bugs.launchpad.net/ubuntu/+source/apt/+bug/245068
-sudo apt-get install libgamin-dev
-sudo apt-get build-dep glib2.0 gtk+2.0
-rm -rf ~/mylibs
-mkdir ~/mylibs
-cd ~/mylibs
-apt-get source glib2.0 gtk+2.0
-cd glib2.0*
-DEB_BUILD_OPTIONS="nostrip noopt debug" debuild
-cd ../gtk+2.0*
-DEB_BUILD_OPTIONS="nostrip noopt debug" debuild
-```
-This should take about an hour.  If it gets stuck waiting for a zombie,
+This should take about an hour. If it gets stuck waiting for a zombie,
 you may have to kill its closest parent (the makefile uses subshells,
-and bash seems to get confused).  When I did this, it continued successfully.
+and bash seems to get confused). When I did this, it continued successfully.
 
 At the very end, it will prompt you for the passphrase for your gpg key.
 
 Then, to run an app with those libraries, do e.g.
-```
-export LD_LIBRARY_PATH=$HOME/mylibs/gtk+2.0-2.16.1/debian/install/shared/usr/lib:$HOME/mylibs/gtk+2.0-2.20.1/debian/install/shared/usr/lib
-```
+
+    export LD_LIBRARY_PATH=$HOME/mylibs/gtk+2.0-2.16.1/debian/install/shared/usr/lib:$HOME/mylibs/gtk+2.0-2.20.1/debian/install/shared/usr/lib
 
 gdb ignores that variable, so in the debugger, you would have to do something like
-```
-set solib-search-path $HOME/mylibs/gtk+2.0-2.16.1/debian/install/shared/usr/lib:$HOME/mylibs/gtk+2.0-2.20.1/debian/install/shared/usr/lib
-```
+
+    set solib-search-path $HOME/mylibs/gtk+2.0-2.16.1/debian/install/shared/usr/lib:$HOME/mylibs/gtk+2.0-2.20.1/debian/install/shared/usr/lib
 
 See also http://sources.redhat.com/gdb/current/onlinedocs/gdb_17.html
 
 ## 64-bit systems
 
-If you're on a 64 bit systems, you can do the above on a 32
+If you're on a 64 bit system, you can do the above on a 32
 bit system, and copy the result.  Or try one of the following:
 
 ### Building your own GTK
 
-```
+```shell
 apt-get source glib-2.0 gtk+-2.0
 
 export CFLAGS='-m32 -g'
 export LDFLAGS=-L/usr/lib32
 export LD_LIBRARY_PATH=/work/32/lib
 export PKG_CONFIG_PATH=/work/32/lib/pkgconfig
 
 # glib
 setarch i386 ./configure --prefix=/work/32 --enable-debug=yes
 
 # gtk
 setarch i386 ./configure --prefix=/work/32 --enable-debug=yes --without-libtiff
 ```
 
+### ia32-libs
 
-### ia32-libs
 _Note: Evan tried this and didn't get any debug libs at the end._
 
 Or you could try this instead:
+
 ```
 #!/bin/sh
 set -x
 set -e
 sudo apt-get build-dep ia32-libs
 rm -rf ~/mylibs
 mkdir ~/mylibs
 cd ~/mylibs
 apt-get source ia32-libs
 cd ia32-libs*
 DEB_BUILD_OPTIONS="nostrip noopt debug" debuild
 ```
 
 By default, this just grabs and unpacks prebuilt libraries; see
-ia32-libs-2.7ubuntu6/fetch-and-build which documents a BUILD
-variable which would force actual building.
-This would take way longer, since it builds dozens of libraries.
-I haven't tried it yet.
+ia32-libs-2.7ubuntu6/fetch-and-build which documents a BUILD variable which
+would force actual building. This would take way longer, since it builds dozens
+of libraries. I haven't tried it yet.
 
 #### Possible Issues
 
 debuild may fail with
+
 ```
 gpg: [stdin]: clearsign failed: secret key not available
 debsign: gpg error occurred!  Aborting....
 ```
-if you forget to create ~/.devscripts with the right contents.
 
-The build may fail with a "FAIL: abicheck.sh" if gold is your system
-linker.  Use ld instead.
+if you forget to create `~/.devscripts` with the right contents.
+
+The build may fail with a `FAIL: abicheck.sh` if gold is your system linker. Use
+ld instead.