When configuring with --enable-gcc-warnings, also enable
-Wjump-misses-init, as it’s confusing to use a goto to skip over
an initialization. Fix the few places in the code that run afoul
of this warning.
* configure.ac (WERROR_CFLAGS): Add -Wjump-misses-init.
* src/doc.c (Fsubstitute_command_keys):
* src/image.c (svg_load_image):
* src/regex.c (re_match_2_internal):
* src/xdisp.c (redisplay_internal, redisplay_window):
Don’t jump over initialization.