MFC r326276:

various: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

MFC r318916: bsdgrep: use safer sizeof() construct

Approved by: emaste (mentor, blanket MFC)

bsdgrep: fix escape map building when using TRE (BSD_GREP_FASTMATCH)

MFC r317700: bsdgrep: use calloc where appropriate in grep's tre-fastmatch

Also apply style(9) to a related NULL check.

MFC r317701: bsdgrep: correct test sense from r317700

Kyle's change in review D10098 was correct. I introduced the error when
extracting a portion of that change.

MFC r317704: bsdgrep: fix escape map building for multibyte strings

In BSD grep, fix escape map building in the regex parser. It was
previously using memory not explicitly initialized, and the MBS escape
map was being built based on a version of the pattern with escapes
already parsed out.

This is Kyle's change, but I restored the broken style that already
exists in this file.

Approved by: emaste (mentor, blanket MFC)

MFC r316495: bsdgrep(1): Fix errors with invalid expressions

Invalid expressions with an ultimate compiled pattern length of 0 (e.g.,
"grep -E {") were not taken into account and caused a segfault while trying
to fill in the good suffix table.

Approved by: emaste (mentor, blanket MFC)

MFC r316492: bsdgrep(1): Rip out "xmalloc" bits

xmalloc was a debug malloc implementation, but the x{malloc,calloc,free}
functions default to calling the malloc(3) equivalents.

Instead of relying on this malloc shim, we can devise better ways to debug
malloc issues that aren't misleading upon initial inspection. (I.e., using
jemalloc's various built-in debugging capabilities.)

Approved by: emaste (mentor, blanket MFC)

MFC r303676:

Fix a segfault in bsdgrep when parsing the invalid extended regexps "?"
or "+" (these are invalid, because there is no preceding operand).

When bsdgrep attempts to emulate GNU grep in discarding and ignoring the
invalid ? or + operators, some later logic in tre_compile_fast() goes
beyond the end of the buffer, leading to a crash.

Fix this by bailing out, and reporting a bad pattern instead.

Approved by: re (gjb, kib)
Reported by: Steve Kargl