Contribution description

• flashpage-test: Fixed print format and removed C preprocessor if statement.
  sizeof(uintptr_t) == sizeof(uint32_t) does not imply PRIx32 == PRIxPTR.
  While it worked for x86-gcc, the arm-gcc resolves uintptr_t to unsigned int and uint32_t to unsigned long.
• sys: Swapped PRIuSIZE format specifiers
• tests-uri_parser.c: Readded missing unsigned cast
• tests-fib.c: Reverting size_t to unsigned type change for add_buf_size due to fib_get_next_hop(..., &add_buf_size, ...) call. I was a bit to eager with this change

Testing procedure

flashpage-test: BOARD=iotlab-m3 make -C tests/periph/flashpage
Others: Compiled all examples and tests for avr-rss2, iotlab-m3, esp32-wroom-32, native and "native64"