Fix for bug in TD_GRID

Fixed typo in grid spacing lookup

See merge request MPIP-Valsson-Group/plumed2-ves!4

All atoms were erroneously requested also after the first step.

when using DEBUG, detailed timers were always shown by mistake.
Now they are only shown when using flag DETAILED_TIMERS

removed sentence about NOSPLINE

https://groups.google.com/d/msgid/plumed-users/4bdade66-5dde-4748-b3c2-3c6155906b69%40googlegroups.com?utm_medium=email&utm_source=footer

added syntax highlight in an example

Small fix: do not push manual when building from a pull request

(see 5c8e4631)

LDSHARED was erroneously reset in configure.

cc: @hanatok

Notice newer cppcheck versions are slower. In order to make the check fit
on travis-ci I had to make a few extra changes:
- better optimization flags when building cppcheck
- force a number of ifdefs in the check

Now master takes approx 25 minutes, so we have room for adding new code.