md_analyze_line: Disallow the strcspn() optiomization path...
md_analyze_line: Disallow the strcspn() optiomization path...

for other platforms then Linux. glibc has well-optimized implementation
which provides good boost, but (as measured one Windows), it can be also
relatively small to our own path below.

We can always enable that path for more platforms, if we get some data
showing it has good impact.

mity/md4c,mity/md4c,mity/md4c