Move the private Pascal headers into libpc where they belong.

diff --git a/h/pc_err.h b/lang/pc/libpc/pc_err.h
similarity index 100%
rename from h/pc_err.h
rename to lang/pc/libpc/pc_err.h

diff --git a/h/pc_file.h b/lang/pc/libpc/pc_file.h
similarity index 100%
rename from h/pc_file.h
rename to lang/pc/libpc/pc_file.h

diff --git a/h/pc_math.h b/lang/pc/libpc/pc_math.h
similarity index 100%
rename from h/pc_math.h
rename to lang/pc/libpc/pc_math.h