Makefile : support DESTDIR for staged installs. Thanks Jorge Aparicio.

Makefile : make install installs both lz4 and lz4c (Jorge Aparicio)
Makefile : removed -Wno-implicit-declaration compilation switch
lz4cli.c : include <stduni.h> for isatty() (Luca Barbato)
lz4.h : introduced LZ4_MAX_INPUT_SIZE constant (Shay Green)
lz4.h : LZ4_compressBound() : unified macro and inline definitions (Shay Green)
lz4.h : LZ4_decompressSafe_partial() : clarify comments (Shay Green)
lz4.c : LZ4_compress() verify input size condition (Shay Green)
bench.c : corrected a bug in free memory size evaluation
cmake : install into bin/ directory (Richard Yao)
cmake : check for just C compiler (Elan Ruusamae)