Align automake usage with upstream's - fixes pkg-config file

The automake usage in the package differed from what upstream does in their boostrap script 0. This resulted in an unusable pkg-config file, containing un-substituted variables, being installed:

$ tail -n2 /usr/lib/pkgconfig/tsk.pc
Requires: @AX_PACKAGE_REQUIRES@
Requires.private: @AX_PACKAGE_REQUIRES_PRIVATE@

To fix this, copy upstream's boostrap script in the build process, after which the pkg-config file looks OK:

$ tail -n2 /usr/lib/pkgconfig/tsk.pc
Requires:
Requires.private: sqlite3 zlib libewf

Resolves: #1 (closed)