CMake: bump version to v0.26

This should be the last version of v0.x series.
This version will contain all the bugs fixed on the legacy branch.

Signed-off-by: Cristina Suteu <cristina.suteu@analog.com>

CMakeLists.txt

@@ -7,7 +7,7 @@ if (MINGW)
 endif()
 
 set(LIBIIO_VERSION_MAJOR 0)
-set(LIBIIO_VERSION_MINOR 25)
+set(LIBIIO_VERSION_MINOR 26)
 set(VERSION "${LIBIIO_VERSION_MAJOR}.${LIBIIO_VERSION_MINOR}")
 if (WIN32)
 	string(TIMESTAMP BUILD_YEAR "%Y")