Work around Linuxisms (#627)

Missed this in my previous tests. Sorry for that.

On BSDs, both bc and sed are part of the base operating system. For sed this results in an error as the check construct (--version) is a GNU-ism and only works for GNU sed, not for bsd sed.
Similarly, BSD sed does not take parameters after the filename(s) operated on. Moving `-i` to the front fixes that. `-r` is provided for GNU compat in BSD sed as an alias of `-E`. The `-i` option in BSD sed requires an extension to work in-place.

(thank you for picking up the nginx module too!)
diff --git a/bootstrap b/bootstrap
index 7c7020d..dbaea15 100755
--- a/bootstrap
+++ b/bootstrap
@@ -2,7 +2,9 @@
 
 REQUIRED='is required, but not installed.'
 bc -v >/dev/null 2>&1 || { echo >&2 "'bc' $REQUIRED"; exit 1; }
+if [ `uname -s` != "FreeBSD" ]; then
 sed --version >/dev/null 2>&1 || { echo >&2 "'sed' $REQUIRED"; exit 1; }
+fi
 autoreconf --version >/dev/null 2>&1 || { echo >&2 "'autoconf' $REQUIRED"; exit 1; }
 
 mkdir m4 2>/dev/null
@@ -21,7 +23,7 @@
 BROTLI_VERSION_PATCH=`expr $BROTLI_VERSION_INT % 4096`
 BROTLI_VERSION="$BROTLI_VERSION_MAJOR.$BROTLI_VERSION_MINOR.$BROTLI_VERSION_PATCH"
 
-sed -r "s/[0-9]+:[0-9]+:[0-9]+/$BROTLI_ABI_INFO/" Makefile.am -i
-sed -r "s/\[[0-9]+\.[0-9]+\.[0-9]+\]/[$BROTLI_VERSION]/" configure.ac -i
+sed -i.bak -r "s/[0-9]+:[0-9]+:[0-9]+/$BROTLI_ABI_INFO/" Makefile.am
+sed -i.bak -r "s/\[[0-9]+\.[0-9]+\.[0-9]+\]/[$BROTLI_VERSION]/" configure.ac
 
 autoreconf --install --force --symlink || exit $