travis: rewrite config file.

Uses CXXFLAGS -O2 instead of default flags to speed up self checking.

Testing is done with the following settings:

1) gcc    CXXFLAGS=-O2
2) gcc    CXXFLAGS=-O2  SRCDIR=build VERIFY=1
3) gcc    CXXFLAGS=-O2  MAKEFLAGS="HAVE_RULES=yes"
4) gcc    CXXFLAGS=-O2  SRCDIR=build VERIFY=1  MAKEFLAGS="HAVE_RULES=yes"
5) clang  CXXFLAGS=-O2
6) clang  CXXFLAGS=-O2  SRCDIR=build VERIFY=1
7) clang  CXXFLAGS=-O2  MAKEFLAGS="HAVE_RULES=yes"
8) clang  CXXFLAGS=-O2  SRCDIR=build VERIFY=1  MAKEFLAGS="HAVE_RULES=yes"

Changes made to before_install:
installe libpcre3

Changes made to script:
* make and make test are now called seperately
* cppcheck also checks "build" folder (created by SRCDIR=build) if existing.
* gui is built twice, one time with HAVE_RULES=yes as qmake argument and one time without it.
* a script has been added and run which returns false if cppcheck --showtime=top5 does not return 7 lines indicating that something is broken


IMPORTANT NOTE: all jobs using "SRCDIR=build" currently fail because errors are reported on the converted files in "build":

[build/checkstl.cpp:1089]: (warning) Assignment of function parameter has no effect outside the function.
[build/checkuninitvar.cpp:2638]: (warning) Assert statement calls a function which may have desired side effects: 'match60'.
I will see if I can suppress these.