Make struct action const
With GCC 4.3.1 on i686, this changes the sizes of sections as follows:
section before after change
.text 682428 682492 +64
.rodata 212668 216352 +3684
.data 58092 54444 -3648
.debug_info
1482388 1482472 +84
.debug_abbrev 153714 153723 +9
.debug_line 272299 272319 +20
.debug_loc 540394 540372 -22
.debug_ranges 113784 113792 +8
Total
3917695 3917894 +199
The surprising .text change comes from src/config/dialogs.o.
Some of that is in get_keybinding_text(), where GCC changes the
order of basic blocks and apparently misses some optimizations.