protobuf-c/: gratuitous style changes

dave's original style drives me crazy. reformat the C code in
protobuf-c/ with "indent -kr -i8" and manually reflow for readability.

try to fit most lines in 80 columns, but due to the lengthy type and
function names in protobuf-c, enforcing an 80 column rule would result
in a lot of cramped statements, so try to fit lines in up to 100 columns
if it would improve readability. (e.g., one <=100 column line is
probably better than 3-4 <=80 column lines.)

ultimately i'd like to adopt most of the recommendations in the linux
coding style: https://www.kernel.org/doc/Documentation/CodingStyle.
this commit gets us most of the kernel indentation and comment coding
style recommendations. later commits will tackle style recommendations
that require more intrusive changes: breaking up large functions,
replacing macros that affect control flow (e.g., DO_ALLOC). this will
hopefully facilitate review and make the code base easier to maintain.

i ran the old and new versions of protobuf-c.c through something like:

  gcc -S -D__PRETTY_FUNCTION__=0 -D__FILE__=0 -D__LINE__=0 -Wall -O0 \
    -o protobuf-c.S -c protobuf-c.c

and reviewed the diffs of the assembly output to spot any functions that
changed, and went back to make sure that any differences were
functionally equivalent.