This mainly changes the indentation level from 8 to 4 spaces,
because I have difficulty working with the wide indents.
There should be no non-whitespace changes here.
Move all global struct definitions to main.h
Merge all global settings into struct settings
Prefix all global variables with _ to emphasize they are global
Reduce variable scope
Make functions static when possible
Make vars const when possible
Make vars unsigned when possible
Use bool type from stdbool.h
Rename some confusingly named variables (i.e. tmp, tmp2)
Prefer stack storage to same-scope malloc/free
Prefer enums for constants
Prefer sprintf to strcat and other tricks
Simplify redundant blocks
Simplify strtok flow
Remove unnecessary parentheses and braces
Replace some magic constants with clearer alternatives
Remove libm dependency (log10 in about.c)
Make highlight logic in interface.c more consistent
Fix wrong item being hashed in digcalc
Remove clear to reduce flicker
Use = {} for zero-initializing
Use calloc instead of malloc/manual zeroing
Make MainQuit be called with an error in a signal handler
Fix file opening modes to match intended use
Read and display error log in window instead of using pager
Remove non-ascii characters from setup.c; replace with hex codes
Recommended header wording copied from https://www.gnu.org/licenses/gpl-howto.html
The only two changes are to use the project name, Snownews,
instead of "this program", to clarify that the entire project is
under the GPL license, rather than only the file with the header.
The second change is to replace snail mail address with the license
URL. It is unreasonable to expect users to send an actual letter to
a US address if the user is in, say, Germany. Postage is expensive.