cache terminal size, add SIGWINCH handler to reset

Refactoring getcols, yet again. We do the following:

1) Introduce a static global in src/pacman/util.c
2) getcols always prefers this cached value, but will derive it from
the COLUMNS environment var, the characteristics of stdout, or a sane
default (in that order).
3) Introduce a SIGWINCH signal handler to reset the cached value,
meaning we only call ioctl when we don't know the value.

On my machine, pacman -Syy goes from ~4300 ioctl calls to 3.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/pacman/util.h b/src/pacman/util.h
index 4a31e89a..b591fbaf 100644
--- a/src/pacman/util.h
+++ b/src/pacman/util.h
@@ -49,7 +49,8 @@ int trans_init(alpm_transflag_t flags, int check_valid);
 int trans_release(void);
 int needs_root(void);
 int check_syncdbs(size_t need_repos, int check_valid);
-unsigned short getcols(int fd);
+unsigned short getcols(void);
+void columns_cache_reset(void);
 int rmrf(const char *path);
 void indentprint(const char *str, unsigned short indent, unsigned short cols);
 size_t strtrim(char *str);