[Libguestfs] enable -Werror and all of gcc's warning options

Here is a bunch of small patches to make fish/ build with most warnings enabled: [1/9] edit.c: avoid warning about signed/unsigned comparison [2/9] fish.c: avoid warnings [3/9] tilde.c: avoid a warning [4/9] fish.c: avoid "assignment discards qualifiers..." warning [5/9] fish.c: avoid signed/unsigned-comparison warning [6/9] fish.c: don't perform arithmetic on void* pointers [7/9] destpaths.c: avoid signed/unsigned-comparison warning [8/9] generator.ml: avoid signed/unsigned-comparison warning in fish/cmds.c [9/9] fish/: enable -Werror and all of gcc's warning options b/fish/Makefile.am | 5 ++--- b/fish/destpaths.c | 3 +-- b/fish/edit.c | 6 +++--- b/fish/fish.c | 2 +- b/fish/fish.h | 2 +- b/fish/rc.c | 3 --- b/fish/tilde.c | 9 +++------ b/src/generator.ml | 5 ++--- fish/fish.c | 9 ++++----- fish/fish.h | 7 ++++++- 10 files changed, 23 insertions(+), 28 deletions(-)