Improved propagation of $(PIKE_SRC_DIR) and $(BUILD_BASE) to modules to

avoid paths containing '..'. The reason is that gcc -MM sometimes seems to
ignore the order of -I arguments and/or do some sort of path simplification.

Rev: src/aclocal.m4:1.39
Rev: src/configure.in:1.567
Rev: src/make_variables.in:1.8
Rev: src/modules/Image/encodings/Makefile.in:1.35
Rev: src/modules/Makefile.in:1.40
Rev: src/modules/_Crypto/lib/Makefile.in:1.31
Rev: src/modules/dynamic_module_makefile.in:1.83
Rev: src/modules/static_module_makefile.in:1.74
Rev: src/post_modules/Makefile.in:1.7