This feature was accidentally removed when doing the initial import from vim. It
makes vim use pipes instead of temporary files for filtering buffers through
shell commands.
I found that this was missing when looking for references of
SHELL_READ/SHELL_WRITE outside mch_call_shell`.
When `mch_call_shell` is reimplemented on top of libuv process management
facilities, pipes will always be used for communication with child processes so
it makes sense to enable the feature permanently.
Because of the '$' in `if(DEFINED $ENV{VALGRIND_CHECK})` EXITFREE wasn't being
defined, so the `free_all_mem` wasn't being included or called in the resulting
binary.
This commit fixes that, and also adds includes needed for `free_all_mem`
compilation.
- Cleanup source tree, leaving only files necessary for compilation/testing
- Process files through unifdef to remove tons of FEAT_* macros
- Process files through uncrustify to normalize source code formatting.
- Port the build system to cmake
