Bump up version number to r55 for release

Add visibility symbols (benhoyt#134)

They are required to properly build DLLs on Windows, and improve the
quality of shared objects on Linux.
See https://gcc.gnu.org/wiki/Visibility for details.

This issue was first discovered here:
mesonbuild/wrapdb#340 (comment)

meson: add static compile args to inih_dep (benhoyt#126)

Signed-off-by: Stephan Lachnit <stephanlachnit@protonmail.com>

Add INI_CUSTOM_ALLOCATOR to allow using a custom memory allocator (be…

…nhoyt#119)

Fixes benhoyt#118

Fix benhoyt#107 (ugh, I thought changing from strncpy was a bad idea)

Use memcpy instead of strncpy to avoid gcc warnings (issue benhoyt#104 …

…and benhoyt#91)

Add options for Meson (benhoyt#103)

* README: initial malloc size before allow realloc
* meson: fix wrong dependency for INIReader
* meson: implement options
* r49 release

r48 release (benhoyt#100)

* Bump copyright to 2020
* Remove makefile for static library
* meson: version 48

Signed-off-by: Stephan Lachnit <stephanlachnit@protonmail.com>

Make INIReader not crash when INI_CALL_HANDLER_ON_NEW_SECTION enabled…

… (name NULL)

Tweak formatting of NULL in README for consistency