maint: accommodate gcc's -Wstrict-overflow option

* src/factor.c (factor_using_pollard_rho): Change type of "i"
to unsigned to avoid warning from gcc's -Wstrict-overflow.
* src/expr.c: Use an unsigned intermediate.
* src/dircolors.c (main): Reorder operations to avoid the risk of
pointer overflow.
* src/tr.c (squeeze_filter): Change NOT_A_CHAR from an anonymous
"enum" to an "int", to avoid this warning:
tr.c:1624:10: error: assuming signed overflow does not occur when
  simplifying conditional to constant [-Werror=strict-overflow]
* src/pr.c (main): Make index "i" unsigned.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/tr.c b/src/tr.c
index 2a729c696..f7593d316 100644
--- a/src/tr.c
+++ b/src/tr.c
@@ -1555,7 +1555,7 @@ squeeze_filter (char *buf, size_t size, size_t (*reader) (char *, size_t))
 {
   /* A value distinct from any character that may have been stored in a
      buffer as the result of a block-read in the function squeeze_filter.  */
-  enum { NOT_A_CHAR = CHAR_MAX + 1 };
+  const int NOT_A_CHAR = INT_MAX;
 
   int char_to_squeeze = NOT_A_CHAR;
   size_t i = 0;