Avoid variable length array (vla) in profit of std::vector

[johannct]

In the lines starting at

lephare/src/lib/onesource.cpp

Line 847 in 86fa1da

double PDFzloc[pdfmap[11].size()];

several VLA are declared. VLA is actually not C++ legal, and -pedantic compilation would fail. It is a G++ extension, and seems to be ok with clang as well.
It turns out that a test using vectors segfaulted the CI in #201 so this was reverted, and the present issue serves as a reminder