Free reflists after usage

Free reflists in cgit_print_branches() and in cgit_print_tags() before
returning reflist structures to the stack.

This fixes following memory leaks seen with "PATH_INFO=/cgit/refs/":

    ==5710== 1,312 (32 direct, 1,280 indirect) bytes in 1 blocks are definitely lost in loss record 63 of 71
    ==5710==    at 0x4C2C04B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==5710==    by 0x4C2C2FF: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==5710==    by 0x46CA9B: xrealloc (wrapper.c:100)
    ==5710==    by 0x40AAA6: cgit_add_ref (shared.c:156)
    ==5710==    by 0x40ABC4: cgit_refs_cb (shared.c:186)
    ==5710==    by 0x44BCBA: do_one_ref (refs.c:527)
    ==5710==    by 0x44D240: do_for_each_ref_in_dir (refs.c:553)
    ==5710==    by 0x44D6BA: do_for_each_ref (refs.c:1298)
    ==5710==    by 0x410FE2: cgit_print_branches (ui-refs.c:191)
    ==5710==    by 0x4111E9: cgit_print_refs (ui-refs.c:244)
    ==5710==    by 0x407C85: refs_fn (cmd.c:105)
    ==5710==    by 0x405DDF: process_request (cgit.c:566)
    ==5710==
    ==5710== 6,846 (256 direct, 6,590 indirect) bytes in 1 blocks are definitely lost in loss record 68 of 71
    ==5710==    at 0x4C2C25E: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==5710==    by 0x46CA9B: xrealloc (wrapper.c:100)
    ==5710==    by 0x40AAA6: cgit_add_ref (shared.c:156)
    ==5710==    by 0x40ABC4: cgit_refs_cb (shared.c:186)
    ==5710==    by 0x44BCBA: do_one_ref (refs.c:527)
    ==5710==    by 0x44D240: do_for_each_ref_in_dir (refs.c:553)
    ==5710==    by 0x44D6EC: do_for_each_ref (refs.c:1288)
    ==5710==    by 0x4110D5: cgit_print_tags (ui-refs.c:218)
    ==5710==    by 0x4111FD: cgit_print_refs (ui-refs.c:246)
    ==5710==    by 0x407C85: refs_fn (cmd.c:105)
    ==5710==    by 0x405DDF: process_request (cgit.c:566)
    ==5710==    by 0x407490: cache_process (cache.c:322)

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>
print_tag_downloads(): Free ref variable

Make sure the ref variable is freed if we build a
"$basename-$version"-style ref.

This fixes following memory leak seen with "PATH_INFO=/cgit/refs/":

    ==8784== 323 bytes in 29 blocks are definitely lost in loss record 41 of 53
    ==8784==    at 0x4C2C04B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==8784==    by 0x56F2DF1: strdup (in /usr/lib/libc-2.17.so)
    ==8784==    by 0x46CA28: xstrdup (wrapper.c:35)
    ==8784==    by 0x410DA6: print_tag_downloads (ui-refs.c:115)
    ==8784==    by 0x410F02: print_tag (ui-refs.c:141)
    ==8784==    by 0x41128B: cgit_print_tags (ui-refs.c:230)
    ==8784==    by 0x41134D: cgit_print_refs (ui-refs.c:250)
    ==8784==    by 0x407C85: refs_fn (cmd.c:105)
    ==8784==    by 0x405DDF: process_request (cgit.c:566)
    ==8784==    by 0x407490: cache_process (cache.c:322)
    ==8784==    by 0x406C18: main (cgit.c:864)

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>
find_default_branch(): Free refmatch after usage

Fixes following memory leak seen with "PATH_INFO=/cgit/refs/":

    ==13408== 7 bytes in 1 blocks are definitely lost in loss record 4 of 52
    ==13408==    at 0x4C2C04B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==13408==    by 0x56F2DF1: strdup (in /usr/lib/libc-2.17.so)
    ==13408==    by 0x46CA78: xstrdup (wrapper.c:35)
    ==13408==    by 0x405840: find_current_ref (cgit.c:426)
    ==13408==    by 0x44BE5A: do_one_ref (refs.c:527)
    ==13408==    by 0x44D3E0: do_for_each_ref_in_dir (refs.c:553)
    ==13408==    by 0x44D85A: do_for_each_ref (refs.c:1298)
    ==13408==    by 0x405889: find_default_branch (cgit.c:438)
    ==13408==    by 0x405AC4: prepare_repo_cmd (cgit.c:490)
    ==13408==    by 0x405D97: process_request (cgit.c:557)
    ==13408==    by 0x407490: cache_process (cache.c:322)
    ==13408==    by 0x406C18: main (cgit.c:864)

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>
cgit_print_tree(): Free curr_rev after usage

Fixes following memory leak seen with "PATH_INFO=/cgit/tree/":

    ==15715== 7 bytes in 1 blocks are definitely lost in loss record 4 of 51
    ==15715==    at 0x4C2C04B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==15715==    by 0x56F2DF1: strdup (in /usr/lib/libc-2.17.so)
    ==15715==    by 0x46CAA8: xstrdup (wrapper.c:35)
    ==15715==    by 0x418A4C: cgit_print_tree (ui-tree.c:274)
    ==15715==    by 0x407D91: tree_fn (cmd.c:131)
    ==15715==    by 0x405E16: process_request (cgit.c:574)
    ==15715==    by 0x4074C8: cache_process (cache.c:322)
    ==15715==    by 0x406C4F: main (cgit.c:872)

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>
cgit_print_commit(): Free tmp variable

Fixes following memory leak seen with "PATH_INFO=/cgit/commit/":

    ==16894== 7 bytes in 1 blocks are definitely lost in loss record 4 of 92
    ==16894==    at 0x4C2C04B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==16894==    by 0x56F2DF1: strdup (in /usr/lib/libc-2.17.so)
    ==16894==    by 0x46CAC8: xstrdup (wrapper.c:35)
    ==16894==    by 0x40CD6F: cgit_print_commit (ui-commit.c:70)
    ==16894==    by 0x407B06: commit_fn (cmd.c:54)
    ==16894==    by 0x405E16: process_request (cgit.c:574)
    ==16894==    by 0x4074C8: cache_process (cache.c:322)
    ==16894==    by 0x406C4F: main (cgit.c:872)

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>
cgit_print_snapshot_links(): Free prefix variable

Fixes following memory leak seen with "PATH_INFO=/cgit/commit/":

    ==16894== 12 bytes in 1 blocks are definitely lost in loss record 9 of 92
    ==16894==    at 0x4C2C04B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    ==16894==    by 0x56F2DF1: strdup (in /usr/lib/libc-2.17.so)
    ==16894==    by 0x46CAC8: xstrdup (wrapper.c:35)
    ==16894==    by 0x414E34: cgit_print_snapshot_links (ui-shared.c:926)
    ==16894==    by 0x40CFA1: cgit_print_commit (ui-commit.c:102)
    ==16894==    by 0x407B06: commit_fn (cmd.c:54)
    ==16894==    by 0x405E16: process_request (cgit.c:574)
    ==16894==    by 0x4074C8: cache_process (cache.c:322)
    ==16894==    by 0x406C4F: main (cgit.c:872)

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>