Massive clang-format of every C or C++ source file (*.h, *.c, *.cpp),
except for:
+ third_party/
+ ext/drsysm/libelftc/include/
+ ext/drsyms/demangle.cc

This is a single, large commit by design to present a single history
disruption point and bring the code base into a consistent format.
clang-format version 6.0 was used.

Tweaks the clang-format rules to indent 4 after pre-processor hashes, to
allow single-line case labels, and align trailing comments.

Disables the pp_indent vera style check as we changed the indent rule and
clang-format now covers it.  Leaves the other checks, even though some are
redundant (they found clang-format errors).

Moves C++ token defines from globals_shared.h and globals.h to a new
header, core/lib/c_defines.h, to avoid a clang-format parsing error where
it fails to identify the include guard.

Adds genapi.pl removal of extra indentation inside API_EXPORT_ONLY and
CLIENT_INTERFACE regions.

Adds exclusions around large regions we don't want to format, in these
files:
+ core/win32/syscallx.h
+ core/arch/x86/decode_table.c
+ core/arch/arm/table_a32_pred.c
+ core/arch/arm/table_a32_unpred.c
+ core/arch/arm/table_t32_16.c
+ core/arch/arm/table_t32_16_it.c
+ core/arch/arm/table_t32_base.c
+ core/arch/arm/table_t32_coproc.c
+ core/arch/arm/table_encode.c

Adds smaller exclusions to work around clang-format bugs:
+ Several missing break-after-return-type
+ Several >90-char lines
+ Misc scattered issues, all listed in #2876

Issue: #2876