Fix a bitwise negation assignment issue spotted by Sun Studio

Change direct and indirect assignments of the bitwise negation of 0 to
uint32_t variables to have a "U" suffix. I.e. ~0U instead of ~0. This
eliminates warnings under Sun Studio 12 Update 1:

    "vcs-svn/string_pool.c", line 11: warning: initializer will be sign-extended: -1 (E_INIT_SIGN_EXTEND)
    "vcs-svn/string_pool.c", line 81: warning: initializer will be sign-extended: -1 (E_INIT_SIGN_EXTEND)
    "vcs-svn/repo_tree.c", line 112: warning: initializer will be sign-extended: -1 (E_INIT_SIGN_EXTEND)
    "vcs-svn/repo_tree.c", line 112: warning: initializer will be sign-extended: -1 (E_INIT_SIGN_EXTEND)
    "test-treap.c", line 34: warning: initializer will be sign-extended: -1 (E_INIT_SIGN_EXTEND)

The semantics are still the same as demonstrated by this program:

    $ cat test.c && make test && ./test
    #include <stdio.h>
    #include <stdint.h>

    int main(void)
    {
        uint32_t foo = ~0;
        uint32_t bar = ~0U;

        printf("foo = <%u> bar = <%u>\n", foo, bar);

        return 0;
    }
    cc     test.c   -o test
    "test.c", line 5: warning: initializer will be sign-extended: -1
    foo = <4294967295> bar = <4294967295>

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

test-treap.c

@@ -31,7 +31,7 @@ static void strtonode(struct int_node *item, const char *s)
 int main(int argc, char *argv[])
 {
 	struct strbuf sb = STRBUF_INIT;
-	struct trp_root root = { ~0 };
+	struct trp_root root = { ~0U };
 	uint32_t item;
 
 	if (argc != 1)

vcs-svn/repo_tree.c

@@ -109,7 +109,7 @@ static struct repo_dirent *repo_read_dirent(uint32_t revision,
 static void repo_write_dirent(const uint32_t *path, uint32_t mode,
 			      uint32_t content_offset, uint32_t del)
 {
-	uint32_t name, revision, dir_o = ~0, parent_dir_o = ~0;
+	uint32_t name, revision, dir_o = ~0U, parent_dir_o = ~0U;
 	struct repo_dir *dir;
 	struct repo_dirent *key;
 	struct repo_dirent *dent = NULL;

vcs-svn/string_pool.c

@@ -8,7 +8,7 @@
 #include "obj_pool.h"
 #include "string_pool.h"
 
-static struct trp_root tree = { ~0 };
+static struct trp_root tree = { ~0U };
 
 struct node {
 	uint32_t offset;
@@ -78,7 +78,7 @@ void pool_print_seq(uint32_t len, uint32_t *seq, char delim, FILE *stream)
 uint32_t pool_tok_seq(uint32_t sz, uint32_t *seq, const char *delim, char *str)
 {
 	char *context = NULL;
-	uint32_t token = ~0;
+	uint32_t token = ~0U;
 	uint32_t length;
 
 	if (sz == 0)