Patch by Jeroen Hoek. See bug 557420 for a prolonged discussion.
Quick summary of the removed sequences:
<Multi_key> <asciicircum> <0>
Consistency. <Multi_key> <asciicircum> [1..9] gives the superscript digit,
legacy sequence for zero is inconsistent.
<Multi_key> <c> <o>
<Multi_key> <c> <O>
Consistency. <Multi_key> <c> [:letter:] already gives vowel plus caron, legacy
sequence for c is inconsistent.
<Multi_key> <comma> <e>
<Multi_key> <comma> <E>
Consistency. <Multi_key> <comma> [:letter:] is for letter with cedilla,
<Multi_key> <semicolon> [:letter:] is for letter with ogolek
<Multi_key> <C> <slash>
<Multi_key> <slash> <C>
Unintuitive. ¢ is visually a vertical bar through a lowercase c, not a slash
through an uppercase C. ₡ has no alternatives, whilst ¢ can be typed as
<Multi_key> <bar> <c>.
<Multi_key> <d> <minus>
đ can be input through <Multi_key> <minus> <d>. <Multi_key> <d> <minus> is used
for ₫.
<Multi_key> <equal> <L>
<Multi_key> <L> <equal>
Unintuitive. ₤ has two dashes, £ one; therefore L + = > ₤, and L + - = £.
<Multi_key> <exclam> <s>
<Multi_key> <exclam> <S>
Consistency. <Multi_key> <exclam> [:letter:] is used for letter with dot below.
§ can be input using <Multi_key> <o> <s>.
<Multi_key> <period> <period>
Might need an alternative for ˙, but … (upstream) has no alternative either.
<Multi_key> <underscore> <a>
<Multi_key> <underscore> <A>
<Multi_key> <underscore> <o>
<Multi_key> <underscore> <O>
Consistency. <Multi_key> <underscore> [:vowel:] gives vowel with macron for ȳ ū
ī ē too.
<Multi_key> <minus> <d>
<Multi_key> <minus> <D>
<Multi_key> <o> <e>
<Multi_key> <O> <E>
Redundant. In upstream as is.
Get gdkkeysyms.h from git, instead of the outdated copy from svn.
Get Unicode 5.2.0 data. Fix a few issues with missing keysyms in
keysyms.txt. Make the filtering of non-BMP keysyms work.
Copying to the clipboard is not a buffer mutation, so calling
gtk_text_buffer_begin_user_action() and _end_user_action() is only
confusing apps which connect to these signals in order to build undo
stacks or otherwise track buffer changes. Most likely, these apps
either didn't notice the bugus undo step or simply work around it.